Reference timing delivery to user equipment with propagation delay compensation

ABSTRACT

A wireless communication system is provided allowing a base station to indicate RTT compensation for UEs to adjust their local time clocks to correct propagation delay timing errors and synchronize with the global clock of a base station. A base station sends a downlink transmission including timing information to a UE and receives an uplink transmission from the UE after the downlink transmission. The base station determines a RTT compensation associated with the timing information based on a RTT between the downlink transmission and the uplink transmission. The base station then transmits the RTT compensation to the UE. UEs are thus allowed to synchronize at a high precision with the time clock of the base station. UEs may be configured with different resolutions or granularities in timing correction so that certain UEs can achieve high precision timing correction while other UEs can adjust their time clocks with less precision.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of U.S. Provisional Application Ser.No. 62/829,545, entitled “REFERENCE TIMING DELIVERY TO USER EQUIPMENTWITH PROPAGATION DELAY COMPENSATION” and filed on Apr. 4, 2019, which isexpressly incorporated by reference herein in its entirety.

BACKGROUND Technical Field

The present disclosure relates generally to communication systems, andmore particularly, to a wireless communication system between a basestation and a user equipment (UE).

Introduction

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,and broadcasts. Typical wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources. Examples of suchmultiple-access technologies include code division multiple access(CDMA) systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, orthogonal frequency divisionmultiple access (OFDMA) systems, single-carrier frequency divisionmultiple access (SC-FDMA) systems, and time division synchronous codedivision multiple access (TD-SCDMA) systems.

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example telecommunication standardis 5G New Radio (NR). 5G NR is part of a continuous mobile broadbandevolution promulgated by Third Generation Partnership Project (3GPP) tomeet new requirements associated with latency, reliability, security,scalability (e.g., with Internet of Things (IoT)), and otherrequirements. 5G NR includes services associated with enhanced mobilebroadband (eMBB), massive machine type communications (mMTC), and ultrareliable low latency communications (URLLC). Some aspects of 5G NR maybe based on the 4G Long Term Evolution (LTE) standard. There exists aneed for further improvements in 5G NR technology. These improvementsmay also be applicable to other multi-access technologies and thetelecommunication standards that employ these technologies.

SUMMARY

The following presents a simplified summary of one or more aspects inorder to provide a basic understanding of such aspects. This summary isnot an extensive overview of all contemplated aspects, and is intendedto neither identify key or critical elements of all aspects nordelineate the scope of any or all aspects. Its sole purpose is topresent some concepts of one or more aspects in a simplified form as aprelude to the more detailed description that is presented later.

The Internet of Things (IoT) allows devices such as UEs to receive,process, and analyze data from a network of other interrelated computingdevices in various consumer and industrial applications (e.g.,telecommunications, automotive, energy, healthcare, etc.). In industrialIoT (IIoT) especially, where UEs may be located in and control processesof oil refineries, power plants, hospitals and the like, timesynchronization between devices is very important. For example, multipleIIoT UEs may communicate with a base station to monitor patients'vitals, etc. If the downlink/uplink subframe timing is not accuratelysynchronized at the base station and the UEs, interference may ariseand/or necessary data may be lost.

Therefore, to accurately synchronize timing between a base station and5G-capable IIOT UEs, a base station may send timing information (e.g., atime-clock) to the UEs based on the IEEE1588v2/Precision Time Protocol.However, under this protocol, the working clock domains of UEs must besynchronized with the global clock of the base station (e.g., thesynchronization master) within ≤1 μs in service areas less than 20 km².This service area condition typically exists in outdoor, macro networkdeployments, where UEs may be hundreds of meters away from the basestation and the propagation delay for transmissions may be large (e.g.,3 μs/km). As such large propagation delays can naturally offset thetiming between the base station and UEs by more than 1 μs, round-triptime (RTT) compensation or propagation delay correction may be neededfor the timing synchronization between base stations and UEs. Althoughglobal positioning system (GPS)-based timing synchronization may providean alternative to the IEEE1588v2/Precision Time Protocol, 5G isadvantageous since it provides a unified system for data communicationand timing.

Hence, there is a need for a solution which allows base stations todeliver timing information to UEs in outdoor scenarios while taking intoaccount RTT compensation to meet the ≤1 μs synchronization accuracyparameter of IEEE1588v2/Precision Time Protocol. There is also a need toprovide this solution for certain UEs (for example, IIOT UEs) whileallowing other UEs (for example, non-IIOT UEs or legacy UEs) to continueto observe less precise timing synchronization parameters.

The present disclosure provides a solution to these needs by allowing abase station to indicate RTT compensation for UEs to use in adjustingtheir individual or local time clocks, thereby allowing UEs tosynchronize at a high precision with the time clock of the base station.The present disclosure further allows UEs to be configured withdifferent resolutions or granularities in timing correction so thatcertain UEs can achieve high precision timing correction while other UEscan adjust their time clocks with less precision. In this way, basestations may deliver timing information to UEs in outdoor scenarioswhile taking into account RTT compensation to meet the ≤1 μssynchronization accuracy parameter of IEEE1588v2/Precision TimeProtocol. Moreover, certain UEs (e.g., IIOT UEs) may obtain higherprecision for timing correction while other UEs (e.g., non-IIOT UEs orlegacy UEs) may observe less precise timing synchronization parameters.

In an aspect of the disclosure, a method, a computer-readable medium,and an apparatus are provided. The apparatus may be a base station. Invarious aspects, the base station sends a downlink transmissionincluding timing information to a UE and receives an uplink transmissionfrom the UE after the downlink transmission. The base station thendetermines a RTT compensation associated with the timing informationbased on a RTT between the downlink transmission and the uplinktransmission. The base station then transmits the RTT compensation tothe UE.

In another aspect of the disclosure, a method, a computer-readablemedium, and an apparatus are provided. The apparatus may be a UE. Invarious aspects, a UE receives a downlink transmission including timinginformation from a base station. The UE sends an uplink transmission tothe base station after the downlink transmission, and obtains a RTTcompensation for the timing information based on a RTT between thedownlink transmission and the uplink transmission.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed, and this description is intended to include all suchaspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a wireless communicationssystem and an access network.

FIGS. 2A, 2B, 2C, and 2D are diagrams illustrating examples of a first5G/NR frame, DL channels within a 5G/NR subframe, a second 5G/NR frame,and UL channels within a 5G/NR subframe, respectively.

FIG. 3 is a diagram illustrating an example of a base station and userequipment (UE) in an access network.

FIG. 4 is a diagram illustrating an example communication flow of timinginformation from one or more base stations to a UE.

FIG. 5 is a diagram illustrating examples of transmission framesrespectively transmitted by a base station and received by a UE.

FIG. 6 is a diagram illustrating various timelines for downlink anduplink transmissions between a base station and UE.

FIGS. 7A and 7B are diagrams illustrating different examples of framestructures in which a base station can provide a UE timing advancecommands.

FIG. 8 is a diagram illustrating an example communication flow between abase station and a UE.

FIG. 9 is a flowchart of a method of wireless communication at a basestation.

FIG. 10 is a conceptual data flow diagram illustrating the data flowbetween different means/components in an example base station apparatus.

FIG. 11 is a diagram illustrating an example of a hardwareimplementation for a base station apparatus employing a processingsystem.

FIG. 12 is a flowchart of a method of wireless communication at a UE.

FIG. 13 is a conceptual data flow diagram illustrating the data flowbetween different means/components in an example UE apparatus.

FIG. 14 is a diagram illustrating an example of a hardwareimplementation for a UE apparatus employing a processing system.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations and isnot intended to represent the only configurations in which the conceptsdescribed herein may be practiced. The detailed description includesspecific details for the purpose of providing a thorough understandingof various concepts. However, it will be apparent to those skilled inthe art that these concepts may be practiced without these specificdetails. In some instances, well known structures and components areshown in block diagram form in order to avoid obscuring such concepts.

Several aspects of telecommunication systems will now be presented withreference to various apparatus and methods. These apparatus and methodswill be described in the following detailed description and illustratedin the accompanying drawings by various blocks, components, circuits,processes, algorithms, etc. (collectively referred to as “elements”).These elements may be implemented using electronic hardware, computersoftware, or any combination thereof. Whether such elements areimplemented as hardware or software depends upon the particularapplication and design constraints imposed on the overall system.

By way of example, an element, or any portion of an element, or anycombination of elements may be implemented as a “processing system” thatincludes one or more processors. Examples of processors includemicroprocessors, microcontrollers, graphics processing units (GPUs),central processing units (CPUs), application processors, digital signalprocessors (DSPs), reduced instruction set computing (RISC) processors,systems on a chip (SoC), baseband processors, field programmable gatearrays (FPGAs), programmable logic devices (PLDs), state machines, gatedlogic, discrete hardware circuits, and other suitable hardwareconfigured to perform the various functionality described throughoutthis disclosure. One or more processors in the processing system mayexecute software. Software shall be construed broadly to meaninstructions, instruction sets, code, code segments, program code,programs, subprograms, software components, applications, softwareapplications, software packages, routines, subroutines, objects,executables, threads of execution, procedures, functions, etc., whetherreferred to as software, firmware, middleware, microcode, hardwaredescription language, or otherwise.

Accordingly, in one or more example embodiments, the functions describedmay be implemented in hardware, software, or any combination thereof. Ifimplemented in software, the functions may be stored on or encoded asone or more instructions or code on a computer-readable medium.Computer-readable media includes computer storage media. Storage mediamay be any available media that can be accessed by a computer. By way ofexample, and not limitation, such computer-readable media can comprise arandom-access memory (RAM), a read-only memory (ROM), an electricallyerasable programmable ROM (EEPROM), optical disk storage, magnetic diskstorage, other magnetic storage devices, combinations of theaforementioned types of computer-readable media, or any other mediumthat can be used to store computer executable code in the form ofinstructions or data structures that can be accessed by a computer.

FIG. 1 is a diagram illustrating an example of a wireless communicationssystem and an access network 100. The wireless communications system(also referred to as a wireless wide area network (WWAN)) includes basestations 102, user equipment (UE) 104, an Evolved Packet Core (EPC) 160,and another core network 190 (e.g., a 5G Core (5GC)). The base stations102 may include macrocells (high power cellular base station) and/orsmall cells (low power cellular base station). The macrocells includebase stations. The small cells include femtocells, picocells, andmicrocells.

The base stations 102 configured for 4G Long Term Evolution (LTE)(collectively referred to as Evolved Universal Mobile TelecommunicationsSystem (UMTS) Terrestrial Radio Access Network (E-UTRAN)) may interfacewith the EPC 160 through first backhaul links 132 (e.g., S1 interface).The base stations 102 configured for 5G New Radio (NR) (collectivelyreferred to as Next Generation RAN (NG-RAN)) may interface with corenetwork 190 through second backhaul links 184. In addition to otherfunctions, the base stations 102 may perform one or more of thefollowing functions: transfer of user data, radio channel ciphering anddeciphering, integrity protection, header compression, mobility controlfunctions (e.g., handover, dual connectivity), inter-cell interferencecoordination, connection setup and release, load balancing, distributionfor non-access stratum (NAS) messages, NAS node selection,synchronization, radio access network (RAN) sharing, multimediabroadcast multicast service (MBMS), subscriber and equipment trace, RANinformation management (RIM), paging, positioning, and delivery ofwarning messages. The base stations 102 may communicate directly orindirectly (e.g., through the EPC 160 or core network 190) with eachother over third backhaul links 134 (e.g., X2 interface). The thirdbackhaul links 134 may be wired or wireless.

The base stations 102 may wirelessly communicate with the UEs 104. Eachof the base stations 102 may provide communication coverage for arespective geographic coverage area 110. There may be overlappinggeographic coverage areas 110. For example, the small cell 102′ may havea coverage area 110′ that overlaps the coverage area 110 of one or moremacro base stations 102. A network that includes both small cell andmacrocells may be known as a heterogeneous network. A heterogeneousnetwork may also include Home Evolved Node Bs (eNBs) (HeNBs), which mayprovide service to a restricted group known as a closed subscriber group(CSG). The communication links 120 between the base stations 102 and theUEs 104 may include uplink (UL) (also referred to as reverse link)transmissions from a UE 104 to a base station 102 and/or downlink (DL)(also referred to as forward link) transmissions from a base station 102to a UE 104. The communication links 120 may use multiple-input andmultiple-output (MIMO) antenna technology, including spatialmultiplexing, beamforming, and/or transmit diversity. The communicationlinks may be through one or more carriers. The base stations 102/UEs 104may use spectrum up to Y MHz (e.g., 5, 10, 15, 20, 100, 400, etc. MHz)bandwidth per carrier allocated in a carrier aggregation of up to atotal of Yx MHz (x component carriers) used for transmission in eachdirection. The carriers may or may not be adjacent to each other.Allocation of carriers may be asymmetric with respect to DL and UL(e.g., more or fewer carriers may be allocated for DL than for UL). Thecomponent carriers may include a primary component carrier and one ormore secondary component carriers. A primary component carrier may bereferred to as a primary cell (PCell) and a secondary component carriermay be referred to as a secondary cell (SCell).

Certain UEs 104 may communicate with each other using device-to-device(D2D) communication link 158. The D2D communication link 158 may use theDL/UL WWAN spectrum. The D2D communication link 158 may use one or moresidelink channels, such as a physical sidelink broadcast channel(PSBCH), a physical sidelink discovery channel (PSDCH), a physicalsidelink shared channel (PSSCH), and a physical sidelink control channel(PSCCH). D2D communication may be through a variety of wireless D2Dcommunications systems, such as for example, FlashLinQ, WiMedia,Bluetooth, ZigBee, Wi-Fi based on the IEEE 802.11 standard, LTE, or NR.

The wireless communications system may further include a Wi-Fi accesspoint (AP) 150 in communication with Wi-Fi stations (STAs) 152 viacommunication links 154 in a 5 GHz unlicensed frequency spectrum. Whencommunicating in an unlicensed frequency spectrum, the STAs 152/AP 150may perform a clear channel assessment (CCA) prior to communicating inorder to determine whether the channel is available.

The small cell 102′ may operate in a licensed and/or an unlicensedfrequency spectrum. When operating in an unlicensed frequency spectrum,the small cell 102′ may employ NR and use the same 5 GHz unlicensedfrequency spectrum as used by the Wi-Fi AP 150. The small cell 102′,employing NR in an unlicensed frequency spectrum, may boost coverage toand/or increase capacity of the access network.

A base station 102, whether a small cell 102′ or a large cell (e.g.,macro base station), may include and/or be referred to as an eNB, gNodeB(gNB), or another type of base station. Some base stations, such as gNB180 may operate in a traditional sub 6 GHz spectrum, in millimeter wave(mmW) frequencies, and/or near mmW frequencies in communication with theUE 104. When the gNB 180 operates in mmW or near mmW frequencies, thegNB 180 may be referred to as an mmW base station. Extremely highfrequency (EHF) is part of the RF in the electromagnetic spectrum. EHFhas a range of 30 GHz to 300 GHz and a wavelength between 1 millimeterand 10 millimeters. Radio waves in the band may be referred to as amillimeter wave. Near mmW may extend down to a frequency of 3 GHz with awavelength of 100 millimeters. The super high frequency (SHF) bandextends between 3 GHz and 30 GHz, also referred to as centimeter wave.Communications using the mmW/near mmW radio frequency band (e.g., 3GHz-300 GHz) has extremely high path loss and a short range. The mmWbase station 180 may utilize beamforming 182 with the UE 104 tocompensate for the extremely high path loss and short range. The basestation 180 and the UE 104 may each include a plurality of antennas,such as antenna elements, antenna panels, and/or antenna arrays tofacilitate the beamforming.

The base station 180 may transmit a beamformed signal to the UE 104 inone or more transmit directions 182′. The UE 104 may receive thebeamformed signal from the base station 180 in one or more receivedirections 182″. The UE 104 may also transmit a beamformed signal to thebase station 180 in one or more transmit directions. The base station180 may receive the beamformed signal from the UE 104 in one or morereceive directions. The base station 180/UE 104 may perform beamtraining to determine the best receive and transmit directions for eachof the base station 180/UE 104. The transmit and receive directions forthe base station 180 may or may not be the same. The transmit andreceive directions for the UE 104 may or may not be the same.

The EPC 160 may include a Mobility Management Entity (MME) 162, otherMMES 164, a Serving Gateway 166, a Multimedia Broadcast MulticastService (MBMS) Gateway 168, a Broadcast Multicast Service Center (BM-SC)170, and a Packet Data Network (PDN) Gateway 172. The MME 162 may be incommunication with a Home Subscriber Server (HSS) 174. The MME 162 isthe control node that processes the signaling between the UEs 104 andthe EPC 160. Generally, the MME 162 provides bearer and connectionmanagement. All user Internet protocol (IP) packets are transferredthrough the Serving Gateway 166, which itself is connected to the PDNGateway 172. The PDN Gateway 172 provides UE IP address allocation aswell as other functions. The PDN Gateway 172 and the BM-SC 170 areconnected to the IP Services 176. The IP Services 176 may include theInternet, an intranet, an IP Multimedia Subsystem (IMS), a PS StreamingService, and/or other IP services. The BM-SC 170 may provide functionsfor MBMS user service provisioning and delivery. The BM-SC 170 may serveas an entry point for content provider MBMS transmission, may be used toauthorize and initiate MBMS Bearer Services within a public land mobilenetwork (PLMN), and may be used to schedule MBMS transmissions. The MBMSGateway 168 may be used to distribute MBMS traffic to the base stations102 belonging to a Multicast Broadcast Single Frequency Network (MBSFN)area broadcasting a particular service, and may be responsible forsession management (start/stop) and for collecting eMBMS relatedcharging information.

The core network 190 may include a Access and Mobility ManagementFunction (AMF) 192, other AMFs 193, a Session Management Function (SMF)194, and a User Plane Function (UPF) 195. The AMF 192 may be incommunication with a Unified Data Management (UDM) 196. The AMF 192 isthe control node that processes the signaling between the UEs 104 andthe core network 190. Generally, the AMF 192 provides QoS flow andsession management. All user Internet protocol (IP) packets aretransferred through the UPF 195. The UPF 195 provides UE IP addressallocation as well as other functions. The UPF 195 is connected to theIP Services 197. The IP Services 197 may include the Internet, anintranet, an IP Multimedia Subsystem (IMS), a PS Streaming Service,and/or other IP services.

The base station may include and/or be referred to as a gNB, Node B,eNB, an access point, a base transceiver station, a radio base station,a radio transceiver, a transceiver function, a basic service set (BSS),an extended service set (ESS), a transmit reception point (TRP), or someother suitable terminology. The base station 102 provides an accesspoint to the EPC 160 or core network 190 for a UE 104. Examples of UEs104 include a cellular phone, a smart phone, a session initiationprotocol (SIP) phone, a laptop, a personal digital assistant (PDA), asatellite radio, a global positioning system, a multimedia device, avideo device, a digital audio player (e.g., MP3 player), a camera, agame console, a tablet, a smart device, a wearable device, a vehicle, anelectric meter, a gas pump, a large or small kitchen appliance, ahealthcare device, an implant, a sensor/actuator, a display, or anyother similar functioning device. Some of the UEs 104 may be referred toas Internet-of-Things (IoT) devices (e.g., parking meter, gas pump,toaster, vehicles, heart monitor, etc.). The UE 104 may also be referredto as a station, a mobile station, a subscriber station, a mobile unit,a subscriber unit, a wireless unit, a remote unit, a mobile device, awireless device, a wireless communications device, a remote device, amobile subscriber station, an access terminal, a mobile terminal, awireless terminal, a remote terminal, a handset, a user agent, a mobileclient, a client, or some other suitable terminology.

Although the present disclosure may focus on 5G NR, the concepts andvarious aspects described herein may be applicable to other similarareas, such as LTE, LTE-Advanced (LTE-A), Code Division Multiple Access(CDMA), Global System for Mobile communications (GSM), or otherwireless/radio access technologies.

Referring again to FIG. 1, in certain aspects, the base station 102/180may include a RTT compensation base station component 198 configured tosend a downlink transmission including timing information to a UE 104.At the base station 102/180, the RTT compensation base station component198 may be further configured to receive an uplink transmission from theUE 104 after the downlink transmission. In addition, the RTTcompensation base station component 198 may be further configured todetermine a round-trip time (RTT) compensation associated with thetiming information based on a RTT between the downlink transmission andthe uplink transmission. The RTT compensation base station component 198may be further configured to transmit the RTT compensation to the UE104.

In certain other aspects, the UE 104 may include a RTT compensation UEcomponent 199 configured to receive the downlink transmission includingtiming information from the base station 102/180. At the UE 104, the RTTcompensation UE component 199 may be further configured to send theuplink transmission to the base station 102/180 after the downlinktransmission. Further, the RTT compensation UE component 199 may beconfigured to obtain a RTT compensation for the timing information basedon a RTT between the downlink transmission and the uplink transmission.

FIG. 2A is a diagram 200 illustrating an example of a first subframewithin a 5G/NR frame structure. FIG. 2B is a diagram 230 illustrating anexample of DL channels within a 5G/NR subframe. FIG. 2C is a diagram 250illustrating an example of a second subframe within a 5G/NR framestructure. FIG. 2D is a diagram 280 illustrating an example of ULchannels within a 5G/NR subframe. The 5G/NR frame structure may be FDDin which for a particular set of subcarriers (carrier system bandwidth),subframes within the set of subcarriers are dedicated for either DL orUL, or may be TDD in which for a particular set of subcarriers (carriersystem bandwidth), subframes within the set of subcarriers are dedicatedfor both DL and UL. In the examples provided by FIGS. 2A, 2C, the 5G/NRframe structure is assumed to be TDD, with subframe 4 being configuredwith slot format 28 (with mostly DL), where D is DL, U is UL, and X isflexible for use between DL/UL, and subframe 3 being configured withslot format 34 (with mostly UL). While subframes 3, 4 are shown withslot formats 34, 28, respectively, any particular subframe may beconfigured with any of the various available slot formats 0-61. Slotformats 0, 1 are all DL, UL, respectively. Other slot formats 2-61include a mix of DL, UL, and flexible symbols. UEs are configured withthe slot format (dynamically through DL control information (DCI), orsemi-statically/statically through radio resource control (RRC)signaling) through a received slot format indicator (SFI). Note that thedescription infra applies also to a 5G/NR frame structure that is TDD.

Other wireless communication technologies may have a different framestructure and/or different channels. A frame (10 ms) may be divided into10 equally sized subframes (1 ms). Each subframe may include one or moretime slots. Subframes may also include mini-slots, which may include 7,4, or 2 symbols. Each slot may include 7 or 14 symbols, depending on theslot configuration. For slot configuration 0, each slot may include 14symbols, and for slot configuration 1, each slot may include 7 symbols.The symbols on DL may be cyclic prefix (CP) OFDM (CP-OFDM) symbols. Thesymbols on UL may be CP-OFDM symbols (for high throughput scenarios) ordiscrete Fourier transform (DFT) spread OFDM (DFT-s-OFDM) symbols (alsoreferred to as single carrier frequency-division multiple access(SC-FDMA) symbols) (for power limited scenarios; limited to a singlestream transmission). The number of slots within a subframe is based onthe slot configuration and the numerology. For slot configuration 0,different numerologies μ 0 to 5 allow for 1, 2, 4, 8, 16, and 32 slots,respectively, per subframe. For slot configuration 1, differentnumerologies 0 to 2 allow for 2, 4, and 8 slots, respectively, persubframe. Accordingly, for slot configuration 0 and numerology μ, thereare 14 symbols/slot and 2μ slots/subframe. The subcarrier spacing andsymbol length/duration are a function of the numerology. The subcarrierspacing may be equal to 2^(μ)*15 kHz, where μ is the numerology 0 to 5.As such, the numerology μ=0 has a subcarrier spacing of 15 kHz and thenumerology μ=5 has a subcarrier spacing of 480 kHz. The symbollength/duration is inversely related to the subcarrier spacing. FIGS.2A-2D provide an example of slot configuration 0 with 14 symbols perslot and numerology μ2 with 4 slots per subframe. The slot duration is0.25 ms, the subcarrier spacing is 60 kHz, and the symbol duration isapproximately 16.67 μs.

A resource grid may be used to represent the frame structure. Each timeslot includes a resource block (RB) (also referred to as physical RBs(PRBs)) that extends 12 consecutive subcarriers. The resource grid isdivided into multiple resource elements (REs). The number of bitscarried by each RE depends on the modulation scheme.

As illustrated in FIG. 2A, some of the REs carry reference (pilot)signals (RS) for the UE. The RS may include demodulation RS (DM-RS)(indicated as R_(x) for one particular configuration, where 100x is theport number, but other DM-RS configurations are possible) and channelstate information reference signals (CSI-RS) for channel estimation atthe UE. The RS may also include beam measurement RS (BRS), beamrefinement RS (BRRS), and phase tracking RS (PT-RS).

FIG. 2B illustrates an example of various DL channels within a subframeof a frame. The physical downlink control channel (PDCCH) carries DCIwithin one or more control channel elements (CCEs), each CCE includingnine RE groups (REGs), each REG including four consecutive REs in anOFDM symbol. A primary synchronization signal (PSS) may be within symbol2 of particular subframes of a frame. The PSS is used by a UE 104 todetermine subframe/symbol timing and a physical layer identity. Asecondary synchronization signal (SSS) may be within symbol 4 ofparticular subframes of a frame. The SSS is used by a UE to determine aphysical layer cell identity group number and radio frame timing. Basedon the physical layer identity and the physical layer cell identitygroup number, the UE can determine a physical cell identifier (PCI).Based on the PCI, the UE can determine the locations of theaforementioned DM-RS. The physical broadcast channel (PBCH), whichcarries a master information block (MIB), may be logically grouped withthe PSS and SSS to form a synchronization signal (SS)/PBCH block. TheMIB provides a number of RBs in the system bandwidth and a system framenumber (SFN). The physical downlink shared channel (PDSCH) carries userdata, broadcast system information not transmitted through the PBCH suchas system information blocks (SIBs), and paging messages.

As illustrated in FIG. 2C, some of the REs carry DM-RS (indicated as Rfor one particular configuration, but other DM-RS configurations arepossible) for channel estimation at the base station. The UE maytransmit DM-RS for the physical uplink control channel (PUCCH) and DM-RSfor the physical uplink shared channel (PUSCH). The PUSCH DM-RS may betransmitted in the first one or two symbols of the PUSCH. The PUCCHDM-RS may be transmitted in different configurations depending onwhether short or long PUCCHs are transmitted and depending on theparticular PUCCH format used. The UE may transmit sounding referencesignals (SRS). The SRS may be transmitted in the last symbol of asubframe. The SRS may have a comb structure, and a UE may transmit SRSon one of the combs. The SRS may be used by a base station for channelquality estimation to enable frequency-dependent scheduling on the UL.

FIG. 2D illustrates an example of various UL channels within a subframeof a frame. The PUCCH may be located as indicated in one configuration.The PUCCH carries uplink control information (UCI), such as schedulingrequests, a channel quality indicator (CQI), a precoding matrixindicator (PMI), a rank indicator (RI), and HARQ acknowledgement(ACK)/negative ACK (HACK) feedback. The PUSCH carries data, and mayadditionally be used to carry a buffer status report (BSR), a powerheadroom report (PHR), and/or UCI.

FIG. 3 is a block diagram of a base station 310 in communication with aUE 350 in an access network. In the DL, IP packets from the EPC 160 maybe provided to a controller/processor 375. The controller/processor 375implements layer 3 and layer 2 functionality. Layer 3 includes a radioresource control (RRC) layer, and layer 2 includes a service dataadaptation protocol (SDAP) layer, a packet data convergence protocol(PDCP) layer, a radio link control (RLC) layer, and a medium accesscontrol (MAC) layer. The controller/processor 375 provides RRC layerfunctionality associated with broadcasting of system information (e.g.,MIB, SIBs), RRC connection control (e.g., RRC connection paging, RRCconnection establishment, RRC connection modification, and RRCconnection release), inter radio access technology (RAT) mobility, andmeasurement configuration for UE measurement reporting; PDCP layerfunctionality associated with header compression/decompression, security(ciphering, deciphering, integrity protection, integrity verification),and handover support functions; RLC layer functionality associated withthe transfer of upper layer packet data units (PDUs), error correctionthrough ARQ, concatenation, segmentation, and reassembly of RLC servicedata units (SDUs), re-segmentation of RLC data PDUs, and reordering ofRLC data PDUs; and MAC layer functionality associated with mappingbetween logical channels and transport channels, multiplexing of MACSDUs onto transport blocks (TBs), demultiplexing of MAC SDUs from TBs,scheduling information reporting, error correction through HARQ,priority handling, and logical channel prioritization.

The transmit (TX) processor 316 and the receive (RX) processor 370implement layer 1 functionality associated with various signalprocessing functions. Layer 1, which includes a physical (PHY) layer,may include error detection on the transport channels, forward errorcorrection (FEC) coding/decoding of the transport channels,interleaving, rate matching, mapping onto physical channels,modulation/demodulation of physical channels, and MIMO antennaprocessing. The TX processor 316 handles mapping to signalconstellations based on various modulation schemes (e.g., binaryphase-shift keying (BPSK), quadrature phase-shift keying (QPSK),M-phase-shift keying (M-PSK), M-quadrature amplitude modulation(M-QAM)). The coded and modulated symbols may then be split intoparallel streams. Each stream may then be mapped to an OFDM subcarrier,multiplexed with a reference signal (e.g., pilot) in the time and/orfrequency domain, and then combined together using an Inverse FastFourier Transform (IFFT) to produce a physical channel carrying a timedomain OFDM symbol stream. The OFDM stream is spatially precoded toproduce multiple spatial streams. Channel estimates from a channelestimator 374 may be used to determine the coding and modulation scheme,as well as for spatial processing. The channel estimate may be derivedfrom a reference signal and/or channel condition feedback transmitted bythe UE 350. Each spatial stream may then be provided to a differentantenna 320 via a separate transmitter 318TX. Each transmitter 318TX maymodulate an RF carrier with a respective spatial stream fortransmission.

At the UE 350, each receiver 354RX receives a signal through itsrespective antenna 352. Each receiver 354RX recovers informationmodulated onto an RF carrier and provides the information to the receive(RX) processor 356. The TX processor 368 and the RX processor 356implement layer 1 functionality associated with various signalprocessing functions. The RX processor 356 may perform spatialprocessing on the information to recover any spatial streams destinedfor the UE 350. If multiple spatial streams are destined for the UE 350,they may be combined by the RX processor 356 into a single OFDM symbolstream. The RX processor 356 then converts the OFDM symbol stream fromthe time-domain to the frequency domain using a Fast Fourier Transform(FFT). The frequency domain signal comprises a separate OFDM symbolstream for each subcarrier of the OFDM signal. The symbols on eachsubcarrier, and the reference signal, are recovered and demodulated bydetermining the most likely signal constellation points transmitted bythe base station 310. These soft decisions may be based on channelestimates computed by the channel estimator 358. The soft decisions arethen decoded and deinterleaved to recover the data and control signalsthat were originally transmitted by the base station 310 on the physicalchannel. The data and control signals are then provided to thecontroller/processor 359, which implements layer 3 and layer 2functionality.

The controller/processor 359 can be associated with a memory 360 thatstores program codes and data. The memory 360 may be referred to as acomputer-readable medium. In the UL, the controller/processor 359provides demultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, and control signalprocessing to recover IP packets from the EPC 160. Thecontroller/processor 359 is also responsible for error detection usingan ACK and/or NACK protocol to support HARQ operations.

Similar to the functionality described in connection with the DLtransmission by the base station 310, the controller/processor 359provides RRC layer functionality associated with system information(e.g., MIB, SIBs) acquisition, RRC connections, and measurementreporting; PDCP layer functionality associated with headercompression/decompression, and security (ciphering, deciphering,integrity protection, integrity verification); RLC layer functionalityassociated with the transfer of upper layer PDUs, error correctionthrough ARQ, concatenation, segmentation, and reassembly of RLC SDUs,re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; andMAC layer functionality associated with mapping between logical channelsand transport channels, multiplexing of MAC SDUs onto TBs,demultiplexing of MAC SDUs from TBs, scheduling information reporting,error correction through HARQ, priority handling, and logical channelprioritization.

Channel estimates derived by a channel estimator 358 from a referencesignal or feedback transmitted by the base station 310 may be used bythe TX processor 368 to select the appropriate coding and modulationschemes, and to facilitate spatial processing. The spatial streamsgenerated by the TX processor 368 may be provided to different antenna352 via separate transmitters 354TX. Each transmitter 354TX may modulatean RF carrier with a respective spatial stream for transmission.

The UL transmission is processed at the base station 310 in a mannersimilar to that described in connection with the receiver function atthe UE 350. Each receiver 318RX receives a signal through its respectiveantenna 320. Each receiver 318RX recovers information modulated onto anRF carrier and provides the information to a RX processor 370.

The controller/processor 375 can be associated with a memory 376 thatstores program codes and data. The memory 376 may be referred to as acomputer-readable medium. In the UL, the controller/processor 375provides demultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, control signal processingto recover IP packets from the UE 350. IP packets from thecontroller/processor 375 may be provided to the EPC 160. Thecontroller/processor 375 is also responsible for error detection usingan ACK and/or NACK protocol to support HARQ operations.

In some aspects, at least one of the TX processor 368, the RX processor356, and the controller/processor 359 may be configured to performaspects in connection with the RTT compensation UE component 199 of FIG.1.

In some other aspects, at least one of the TX processor 316, the RXprocessor 370, and the controller/processor 375 may be configured toperform aspects in connection with the RTT compensation base stationcomponent 198 of FIG. 1.

IoT allows devices, such as UEs, to receive, process, and analyze datafrom a network of other interrelated computing devices in variousconsumer and industrial applications (e.g., telecommunications,automotive, energy, healthcare, etc.). In industrial IoT (IIoT)especially, where UEs may be located in and control processes of oilrefineries, power plants, hospitals and the like, time synchronizationbetween devices is very important. For example, multiple IIoT UEs maycommunicate with a base station to monitor patients' vitals, etc. If thedownlink/uplink subframe timing is not accurately synchronized at thebase station and the UEs, interference may arise and/or important datamay be lost.

Therefore, to accurately synchronize timing between a base station and5G-capable IIOT UEs, a base station may send timing information (e.g., atime-clock) to the UEs based on the IEEE1588v2/Precision Time Protocol.However, under this protocol, the working clock domains of UEs must besynchronized with the global clock of the base station (e.g., thesynchronization master) within ≤1 μs in service areas less than 20 km².This service area parameter typically exists in outdoor, macro networkdeployments, where UEs may be hundreds of meters away from the basestation and the propagation delay for transmissions may be large (e.g.,3 μs/km). As such large propagation delays can naturally offset thetiming between the base station and UEs by more than 1 RTT compensationor propagation delay correction may be needed for the timingsynchronization between base stations and UEs. Although globalpositioning system (GPS)-based timing synchronization may provide analternative to the IEEE1588v2/Precision Time Protocol, 5G NR isadvantageous since 5G NR provides a unified system for datacommunication and timing.

Hence, a need exists for a solution which allows base stations todeliver timing information to UEs in outdoor scenarios while taking intoaccount RTT compensation to meet the ≤1 μs synchronization accuracyparameter of IEEE1588v2/Precision Time Protocol. A need also exists toprovide a similar solution to certain UEs (for example, IIOT UEs) whileallowing other UEs (for example, non-IIOT UEs and/or legacy UEs) tocontinue to observe less precise timing synchronization parameters.

The present disclosure provides various approaches and solutions to theaforementioned needs by allowing a base station to indicate RTTcompensations to UEs to use in adjusting individual or local timeclocks, thereby allowing UEs to relatively precisely synchronize withthe time clock of the base station. The present disclosure furtherprovides for UEs to be configured with different resolutions orgranularities in timing correction so that certain UEs can achievehighly precise timing corrections while other UEs can adjust their timeclocks with less precision. In this way, base stations may delivertiming information to UEs in outdoor scenarios while taking into accountRTT compensation to meet the ≤1 μs synchronization accuracy parameter ofIEEE1588v2/Precision Time Protocol. Moreover, certain UEs (e.g., IIOTUEs) may obtain higher precision for timing correction while other UEs(e.g., non-IIOT UEs or legacy UEs) may observe less precise timingsynchronization parameters.

FIG. 4 is a diagram 400 illustrating an example communication flow oftiming information 402 from one or more base stations 404 (e.g., basestation 180) to a UE 406 (e.g., base station 102). The base station 404may communicate with a 5G core network 408 (e.g., core network 190) viaa N2 interface (e.g., through AMF 192) and/or a N3 interface (e.g.,through UPF 195). The base station 404 may also communicate with the UE406 over a wireless link or Uu interface, while the 5G core network 408may communicate directly with the UE 406 via a N1 interface. The basestation 404 and 5G core network may be components of a 5G corearchitecture 410.

A time-sensitive network (TSN) system 412 may be connected to the 5Gcore network 408. The TSN 412 may include a grandmaster clock 414serving as the global clock for the base station 404. The TSN system 412may be connected to the 5G core architecture 410 via a TSN link 416. TheUE 406 includes the local clock 418 of the UE 406.

To synchronize the timing of the base station 404 and the UE 406, thebase station first receives the timing information 402 from thegrandmaster clock 414 and then provides the timing information 402 tothe UE over a 5G air interface. In this way, the UE 406 can synchronizethe local clock 418 or working clock(s) with the global clock of thebase station 404.

FIG. 5 illustrates a diagram 500 illustrating examples of transmissionframes 502 a, 502 b respectively transmitted by a base station 504 andreceived by a UE 506. When the base station 504 sends a transmissionframe 502 a including timing information 507 (e.g., timing information402 received from TSN 412), the UE 506 may receive the correspondingtransmission frame 502 b including the timing information after apropagation delay 508. In certain aspects, the UE 506 may compensate forthe propagation delay 508 based on whether the timing information 507 isbroadcast or unicast to the UE 506.

In one aspect, timing information 507 received from the TSN (e.g., TSN412) may be commonly broadcast to multiple UEs 506. In some aspects, thetiming information 507 may include information associated with one ormore symbols and/or one or more slots 510 at the beginning of frames 502a, 502 b. For example, the timing information 507 may indicate a pointerto frame number, which is used by the UE 506 to derive the frame numberwhich is the beginning of a downlink transmission. In some aspects, thebeginning of the frame may refer to the first symbol of that frame,which may be the first symbol of that frame (e.g., first OFDM symbol).While the timing information 507 may be illustrated as occurring at thebeginning of a frame, the timing information 507 may be carried in otherlocations (e.g., symbols) of a frame that are not necessarily at thebeginning of the frame. The base station 504 may broadcast the timinginformation 507 in a SIB at a 40 nanosecond (ns) resolution. Each UE 506receiving the broadcast message may subsequently adjust their localclock (e.g., local clock 418 in FIG. 4) based on a compensation forpropagation delay 508 received from the base station 504.

In some other aspects, timing information 507 may be unicast toindividual UEs 506 that need the timing information (for example, forindividual applications). The timing information 507 may indicateinformation associated with the beginning of frames 502 a, 502 b. Theunicast message may be typically sent via an RRC protocol (for example,in RACH). When unicast signaling is used, as each UE has their own localclock (e.g., local clock 418 in FIG. 4), potentially different timinginformation 507 with different compensations for propagation delay 508may be individually sent to different UEs 506. In certain aspects, theUEs 506 may adjust their local clocks based on an estimate ofpropagation delay 508 which is known to base station 504.

In one example, referring to FIGS. 4 and 5 according to a first aspectof the present disclosure, the base station 404, 504 or networkindicates the timing information 402, 507 (e.g., a common system timing)via unicast or broadcast signaling to UE 406, 506. The timinginformation 507 may indicate information associated with one or moresymbols and/or slots at the beginning of a downlink transmission (e.g.,frame 502 a). The UE 406, 506 receives the downlink transmission (e.g.,frame 502 b) (e.g., based on the timing information 402, 507) from thebase station 404, 504 after a propagation delay 508 from the transmittedframe 502 a. The UE 406, 506 may subsequently send an uplinktransmission. Based on a RTT between the downlink and uplinktransmissions, the base station 404, 504 may send a RTT compensation tothe UE 406, 506. The timing information 402, 507 may be transmitted withthe RTT compensation. In one aspect, the RTT compensation may be atiming advance (TA) 512 within a TA command. For example, the basestation 404, 504 may transmit, and the UE 406, 506 may receive, the RTTcompensation within a TA command in a random access response (RAR) of aRACH procedure.

After receiving the TA command with the RTT compensation, the UE 406,506 adjusts the local clock 418 with the timing advance 512 and deliversthe adjusted time to the upper layers 514 of the UE 406, 506 (e.g.,layer 2 and/or layer 3). For example, the UE 406, 506 may deliver anadjusted time to the upper layers 514 based on the following formulaafter receiving a broadcast timing information 402, 507:Time Delivered to Upper Layer=Broadcasted Time+“Applied TA Advance”/2,whereBroadcasted Time is the UE reception timing of the downlink transmissionindicating the timing information 402, 507 after the propagation delay508; and “Applied TA Advance” is the timing advance 512 indicated in theTA command.

Thus, in one aspect, a UE may generally use a timing advance frameworkto compensate for and/or correct a lack of timing synchronicity causedby the propagation delay between a base station and the UE. Certainaspects related to the timing advance are described below with respectto FIGS. 6, 7A, and 7B and accompanying description. In another aspect,a UE may use a separate procedure independent from a TA to correcttiming synchronicity between a base station and the UE. Certain aspectsrelated to this other aspect are described below with respect to FIG. 8and accompanying description.

In various aspects, the base station may indicate an RTT compensation tothe UE. The RTT compensation may include, for example, a TA within a TAcommand, a timing offset between a base station transmission timelineand a base station reception timeline, an estimated time differencebetween a base station transmission timing and a base station receptiontiming, and/or an actual time difference between a base stationtransmission timing and a base station reception timing and a UEtransmission timing and a UE reception timing.

FIG. 6 shows a diagram 600 illustrating various timelines for downlinkand uplink transmissions between a base station 602 and UE 604. Inparticular, the base station 602 sends downlink transmissions accordingto a base station transmission timeline 606, while the base stationreceives uplink transmissions according to a base station receptiontimeline 608. Similarly, the UE 604 sends uplink transmissions accordingto a UE transmission timeline 610, while the UE receives downlinktransmissions according to a UE reception timeline 612. In one aspect,in order to synchronize the timing information (e.g., timing information402, 507) corresponding to the UE and base station timelines, the basestation 602 may send an RTT compensation (e.g., one or more TAs in oneor more TA commands) to the UE 604. Based on the RTT compensationreceived from the base station 602, the UE 604 may control the timing ofthe UE transmission and reception timelines 610, 612 relative to thebase station transmission and reception timelines 606, 608.

Generally, the base station transmission timeline 606 and the basestation reception timeline 608 are aligned. However, in certain aspects,the timelines 606, 608 may be offset. For example, FIG. 6 illustrates atiming offset 614 or TA error (e.g., referred to as a gNBRxOffset orsome other name) between the base station transmission timeline 606 andbase station reception timeline 608. The base station 602 may adjust thebase station reception timeline 608 to be offset from the base stationtransmission timeline 606 (e.g., using separate processors) in caseswhere, for instance, the UE 604 needs extra time to decode a downlinktransmission and provide ACK than the base station 602 may need todecode an uplink transmission and provide ACK. The base station 602 mayalso include timing offset 614 in frequency division duplex (FDD)systems where there may be no inherent parameter for the base stationtransmission timeline 606 and base station reception timeline 608 to beexactly aligned, and/or in time division duplex (TDD) systems where thebase station may flexibly align the timelines 606, 608 with any timingoffset 614 subject to both timelines being within a guard period in thebandwidth of a transmission channel.

In certain aspects, the base station transmission timeline 606 and thebase station reception timeline 608 are aligned within a guard periodwhen base station 602 and UE 604 communicate in a TDD mode. In otheraspects, the uplink transmissions from multiple UEs 604 may be receivedby the base station 602 within the CP of a subsequent downlinktransmission in either the TDD mode or a FDD mode. In additionalaspects, the timing advance command may request an individual UE 604 toadvance or delay a UE transmission timelines 610 to synchronize with thetiming of the base station 602.

In one example referring to FIG. 6, a base station 602 sends a downlinktransmission including timing information and RTT compensation at timet1 in the transmission timeline 606. The time t1 may be synchronized tothe grandmaster clock (e.g., grandmaster clock 414) and may be indicatedin the timing information (e.g., timing information 402, 507). The RTTcompensation may be equal to the timing advance 603 included in a TAcommand. After a downlink propagation delay 616, the UE 604 subsequentlyreceives the downlink transmission at time t2 in the reception timeline612. As illustrated in FIG. 6 with respect to the downlink transmission,the UE reception timeline 612 is offset from the base stationtransmission timeline 606 by downlink propagation delay 616.

To compensate for this offset, the UE 604 applies the RTT compensation(e.g., the received timing advance 603) to the local clock such that theUE transmission timeline 610 is advanced with respect to the basestation reception timeline 608. As shown in FIG. 6 at time t3, the UEtransmission timeline 610 is advanced with respect to the base stationreception timeline 608. The UE 604 then transmits the uplinktransmission at time t3 in the transmission timeline 610. After anuplink propagation delay 618, the base station 602 subsequently receivesthe uplink transmission at time t4 in the reception timeline 608.

As a result, the local clock of the UE 604 may be synchronized with theglobal clock of the base station 602 using the RTT compensation.Although the base station reception timeline 608 may be aligned with thebase station transmission timeline 606, the timelines 606, 608 mayinclude a timing offset 614 in some other aspects, as illustrated inFIG. 6. Potentially, when the base station reception timeline 608 isaligned with the base station transmission timeline 606, the downlinkpropagation delay 616 is generally the same as the uplink propagationdelay 618. As a result, the RTT compensation applied by the UE 604 maygenerally be twice the propagation delay 616 or the propagation delay618.

FIGS. 7A and 7B illustrate different examples of frame structures inwhich a base station can provide a UE TA commands. For example, FIG. 7Aillustrates an example of a MAC-Control Element (CE) (MAC-CE 700)including a 6-bit TA command 702 (e.g., maximum 6-bit TA command) and atiming advance group ID (TAG-ID) 704. Further, FIG. 7B illustrates anexample of an RAR 750 including a 12-bit TA command 752 (e.g., maximum12-bit TA command). The number of bits (e.g., (e.g., maximum number ofbits) shown for the timing advance commands in FIGS. 7A and 7B areillustrative, and other numbers besides 6 or 12 bits for the TA commandsmay be used.

The base station (e.g., base station 602) may deliver a different valuefor the RTT compensation to the UE (e.g., UE 604) based on the framestructure used for the TA. In one example, if the UE is in connectedmode and actively receiving communication from the base station, thebase station may transmit and the UE may receive the MAC-CE 700indicating the 6-bit TA command 702. In another example, if the UE isinitially connecting to the base station (e.g., via RACH) or waking froma power save mode, the base station may transmit and the UE may receivethe RAR 750 indicating the 12-bit TA command. The TA command 702 forMAC-CE 700 may have an index value between −31 and +31, while the TAcommand 752 for RAR 750 may have an index value between −2048 and +2048.

The TA applied by the UE is based on a TA index value (e.g., a value ofthe 6-bit or 12-bit TA command illustrated in FIG. 7A or 7B) and a TAgranularity. The TA granularity indicates a time (T_(s)) by which the TAindex value is multiplied in order to obtain the TA (e.g., TA 603 inFIG. 6). For example, assuming a 15 kHz subcarrier spacing (SCS), the TAgranularity may be 16*64 T_(s), where T_(s)=1/(64*30.72) μs (in total,approximately 0.52 μs). Since the TA command 702 of MAC-CE 700 has amaximum index value of +31, the TA delivered in MAC-CE 700 may have amaximum value of 31*0.52 μs, or approximately 16 μs, and a minimumabsolute non-zero value of 1*0.52 μs, or approximately 0.52 μs or 520ns. Thus, referring to FIG. 6 in one example, when the UE 604 receivesthe downlink transmission including the timing information and a TA 603at time t2, assuming a TA granularity associated with a 15 kHz SCS and aTA index value of 2, the UE 604 may advance the UE transmission timeline610 by approximately 1 μs or 1000 ns with respect to the global clock ofthe base station 602.

The TA granularity may be a function of the SCS used in communicationbetween the base station and the UE. As 5G includes multiple SCS,different TA granularities may be applied to obtain the TA depending onthe SCS. Table 1 illustrates an example of various TA granularities fordifferent SCS in 5G:

TABLE 1 Subcarrier Spacing (kHz) of First Uplink Transmission After RARTiming Advance Granularity 15 16*64 T_(s) 30  8*64 T_(s) 60  4*64 T_(s)120  2*64 T_(s)

Thus, referring again to the example above concerning FIG. 6, if the SCSwas changed from 15 kHz to 30 kHz with the TA index value of 2, the UE604 may advance the UE transmission timeline 610 by approximately 0.5 μswith respect to the global clock of the base station 602. In some otheraspects, if the SCS was changed to 120 kHz, the UE 604 may advance theUE transmission timeline 610 by approximately 0.125 μs.

Thus, UEs may adjust their local clocks to synchronize with the globalclock of the base station using TA as an RTT compensation for thepropagation delay between the base station and the UE. However, certainUEs (e.g., IIOT UEs) may need a higher timing synchronization accuracyto meet the ≤1 μs parameter of IEEE1588v2/Precision Time Protocol thanthe aforementioned TA granularity provides. Moreover, other UEs (e.g.,legacy UEs) may not need to receive timing information with highprecision synchronization parameters from the base station. Therefore,in one aspect of the present disclosure, finer, UE-specific TAgranularity may be provided to increase synchronization accuracy forIIOT UEs, while the aforementioned granularity and TA procedure forlegacy UEs may be maintained.

In various aspects, the base station (e.g., base station 602) or networkmay configure a UE-specific TA granularity. Thus, different TAgranularities may be configured for different UEs. For example, an IIOTUE may be configured with a finer (e.g., smaller) TA granularityassociated with a SCS than that of a legacy UE. Moreover, theUE-specific TA granularity may be different than any of the TAgranularities indicated in Table 1 above.

In various aspects, the UE (e.g., UE 604) may report a UE identity aseither an IIOT UE or a legacy UE to the base station (e.g., base station602) or another network node (for example, during a SRS, RACH, or otheruplink transmission). Depending on the reported identity of the UE, thebase station may configure or indicate UE-specific TA granularities. Forexample, if the base station receives a message from the UE including anidentification as a legacy UE, the base station may configure the UEwith a TA granularity in accordance with Table 1. In another example, ifthe base station receives a message from the UE including anidentification as an IIOT UE, the base station may indicate to the UE aUE-specific TA granularity which is finer than those indicated above inTable 1. In other examples, the base station may indicate identical orlarger TA granularities to IIOT UEs compared to legacy UEs.

In one aspect, the UE-specific TA granularity may be configuredseparately from the TA command. For example, different TA granularitiesmay be provided without changing the maximum size or header of the TAcommand 702, 752 in MAC-CE 700 or RAR 750. Rather, the network mayconfigure another set of TA granularities different from those in Table1 for UEs to apply to identical TA commands. For example, IIOT UEs maybe configured with a different TA granularity than legacy UEs (e.g., 64T_(s) or other granularity smaller than those in Table 1) depending onthe SCS for communication between the base station and UE. In anotherexample, legacy UEs may request the base station or network to configurethe UEs with a UE-specific TA granularity which may be different thanother UEs. In this way, a base station may send the same TA command toIIOT UEs and legacy UEs, while allowing for UEs configured withdifferent TA granularities to use different TAs for adjusting theirlocal clock (e.g., finer or smaller TAs—e.g., approximately 15 or 30 nsas opposed to 1 μs for IIOT UEs).

In accordance with this aspect, a base station may determine to sendmultiple TA commands often to UEs configured with UE-specific TAgranularities. For example, the base station may send multiple TAcommands to achieve a certain TA precision for an IIOT UE or other UEconfigured with a UE-specific TA granularity. This situation may arise,for example, when an IIOT UE configured with a smaller TA granularitythan that of Table 1 has moved farther away from the base station orexperiences radio frequency interference, increasing the propagationdelay, and therefore, incurring multiple TA commands to compensate forthe delay. However, this situation may result in a “slamming” effectwhere the base station may need to “slam” an IIOT UE with multiple TAcommands to achieve the same result that a single TA command couldaccomplish for a legacy UE (e.g., a 1 μs TA). Nevertheless, by fixingthe maximum size or header of the TA command 702, 752 in MAC-CE 700 orRAR 750, this aspect limits the slamming effect based on the maximumindex value available for the TA command.

In another aspect, the base station may dynamically indicate UE-specificTA granularities in downlink transmissions. The UE-specific TAgranularities may be implemented by different TA commands used inconnection with sending timing information to the UE. For example, thebase station or network may configure MAC-CE 700 to have a new header ora larger size TA command which is transmitted to IIOT UEs separatelyfrom other TA commands. The increase in size may allow a base stationtransmitting the MAC-CE to convey to certain UEs higher resolutions(e.g., more precision) of TAs via a larger span of TA index values. Insome other aspects, the size of the TA command may not be increased, andthe base station may transmit MAC-CEs with different header values toconvey to UEs higher resolutions of TAs via different TA granularities.

For example, one or more bits in the TA Command 702 of MAC-CE 700 may beused to designate the TA as being based on a first set of TAgranularities (e.g., as shown for example in Table 1) or based on asecond set of finer TA granularities. In another example, one of thevalues of the TAG ID 704 of MAC-CE 700 may be used to designate thefirst or second set of TA granularities. In a further example, a newMAC-CE with different size or header values than MAC-CE 700 may beprovided to UEs receiving TAs based on the second set of TAgranularities. Thus, the aforementioned “slamming” effect may be limitedthrough use of separate TA commands for UEs with UE-specific TAgranularities, due to the base station not needing to repeatedly sendcommon TA commands to these UEs.

In another aspect, referring to FIG. 6, the TA 603 received and appliedby the UE (e.g., an IIOT UE) may be based on the timing offset 614between the base station transmission timeline 606 and base stationreception timeline 608. Thus, referring to FIGS. 4 and 5, afterreceiving the TA command with the RTT compensation (e.g., TA 512), theUE 406, 506 may adjust the local clock 418 with the TA 512 based as wellon the timing offset 614. In this case, the UE 406, 506 may deliver anadjusted time to the upper layers 514 based on the following formulaafter receiving a broadcast timing information 402, 507:Time Delivered to Upper Layer=Broadcasted Time+“Applied TAAdvance”/2−gNBRxOffset, where:

Broadcasted Time is the UE reception timing of the downlink transmissionindicating the timing information 402, 507 after propagation delay 508;

Applied TA Advance is the TA 512 indicated in the TA command; and

gNBRxOffset is the timing offset 614 between the base stationtransmission timeline 606 and base station reception timeline 608.

In various aspects, the base station may indicate the timing offset 614to the UE via a separate message from the timing information, ratherthan applying the timing offset 614 to the broadcasted timinginformation advertised by the base station. This separate messagetransmitted by the base station may be, for example, a physical layer(PLY) message, a layer 2 MAC message, or a layer 3 RRC message. Thus,when a base station transmits timing information to UE 604 correspondingto the value t1 in the base station transmission timeline, the basestation may allow the UE to calculate the correct timing informationusing the TA by indicating the timing offset 614. In this way, legacyUEs or other UEs will not necessarily need to receive broadcast timinginformation with applied RTT compensation if they do not need highprecision time synchronization.

Referring now to FIG. 8, in a second aspect of the present disclosure,the base station or network indicates the timing information (e.g., anabsolute time) including the RTT compensation to the UE via a separateand independent procedure from the TA command. FIG. 8 shows a diagram800 illustrating an example communication flow between a base station802 and a UE 804 in accordance with this second aspect of the presentdisclosure. In one aspect, the RTT compensation is UE-specific, and thetiming information may be delivered to the UE via unicast signaling.

The base station 802 first sends a downlink transmission 806 at time t0,corresponding to the start of a frame boundary from the perspective ofthe base station. The downlink transmission 806 may include timinginformation corresponding to the absolute time provided by thegrandmaster clock (e.g., timing information 507 in FIG. 5). The UE 804subsequently receives the downlink transmission 806 at time t1,corresponding to the start of a frame boundary from the perspective ofthe UE. The UE then transmits an uplink transmission 808 at time t2. Theuplink transmission 808 may be, for example, a SRS waveform (e.g., whenthe UE 804 is in connected mode) or a RACH waveform (e.g., when the UE804 is in idle mode). The base station 802 subsequently receives theuplink transmission 808 at time t3.

In one aspect, the base station 802 may explicitly communicate the RTTbetween the fixed time, t0, and time the base station received theuplink transmission, t3, independently from TA commands. For example, inFIG. 8, the value A represents the base station time difference 810between t3 and t0, while the value B represents the UE time difference812 between t2 and t1. The UE may determine the RTT, and thus thepropagation delay, based on the values of A and B. In one aspect, thebase station estimates the value A by calculating the difference betweent3 and t0, and sends the value A to the UE in a message. For example,the base station may send the value A in the downlink transmission 806.As the value B is known the UE, the UE may calculate the RTT bysubtracting the value B from the received value A from the base station.The UE may then divide the RTT by two to obtain the one-way propagationdelay, which the UE may use to adjust the timing information receivedfrom the base station to synchronize the local clock with the globalclock.

In this way, the base station 802 or network may indicate, in a separatemessage from the TA command, the value A as the RTT compensation for UE804 to use for timing synchronization. The message including the value Amay be, for example, a PLY message, a layer 2 MAC message or a layer 3RRC message transmitted by the base station to the UE. In contrast to TAcommand 702 or 752 (see FIG. 7), which may be limited in size to a smallnumber of bits, the message including the value A may not be so limited,and could therefore range in the tens of nanoseconds, for example. Thus,the value A has higher granularity or precision for timing adjustmentthan the TA command, which may be constrained in size to the larger,microsecond range as described above. Moreover, the message includingthe value A can be sent less often than the TA command, avoidingslamming effect concerns.

Moreover, once the UE obtains the timing information with the RTTcompensation (e.g., the value A), the UE may determine to adjust thetiming information based on the propagation delay derived from the RTTcompensation and the value B as described above. Thus, this aspect ofthe present disclosure allows a different framework than TA to be usedto communicate the RTT compensation to the UE.

In another aspect, the UE 804 may indicate the value B to the basestation 802, and the base station may determine the RTT compensation forthe UE to use in timing synchronization. For example, after the UEreceives at time t1 the downlink transmission 806, the UE 804 maytransmit at time t2 to the base station 802 the value B in uplinktransmission 808. Once the base station receives the value B, the basestation may obtain the RTT and thus the propagation delay by calculatingthe actual value A and subtracting the UE-indicated value B.

The base station 802 or network may then provide the RTT compensation(e.g., the difference between the values of A and B) to the UE 804 basedon whether the downlink transmission 806 including the timinginformation (e.g., the grandmaster clock time) was broadcast or unicastto the UE 804. In one aspect, if the downlink transmission 806 wasbroadcast to UE 804, the base station 802 may provide the RTTcompensation to the UE 804 for the UE 804 to adjust the UE local clockto synchronize the timing information. For example, the RTT compensationmay be broadcast to a plurality of UEs. In another aspect, if thedownlink transmission 806 is unicast to UE 804, the base station 802 mayeither provide the RTT compensation to the UE 804 (e.g., as discussedabove), or adjust the timing information with the RTT compensation andsend the adjusted timing information to the UE 804.

FIG. 9 is a flowchart 900 of a method of wireless communication. Themethod may be performed by a base station (e.g., the base station 102,310, 404, 504, 602, 802; the apparatus 1002/1002′; the processing system1114, which may include the memory 376 and which may be the entire basestation 102, 310, 404, 504, 602, 802 or a component of the base station102, 310, 404, 504, 602, 802, such as the TX processor 316, the RXprocessor 370, and/or the controller/processor 375). Optional aspectsare illustrated in dashed lines. The method allows a base station toindicate RTT compensation for UEs to use in adjusting their individualor local time clocks, thereby allowing UEs to synchronize at a highprecision with the time clock of the base station. The presentdisclosure further allows UEs to be configured with differentresolutions or granularities in timing correction so that certain UEscan achieve high precision timing correction while other UEs can adjusttheir time clocks with less precision.

At 902, the base station receives the timing information from a TSN. Forexample, 902 may be performed by the reception component 1004 of FIG.10. For example, referring to FIG. 4, to synchronize the timing of thebase station 404 and the UE 406, the base station 404 receives thetiming information 402 from the grandmaster clock 414 and then providesthe timing information 402 to the UE 406 (e.g., over a 5G airinterface). The TSN 412 may include the grandmaster clock 414, whichserves as the global clock for the base station 404.

At 904, the base station sends a downlink transmission including timinginformation to a UE. For example, 904 may be performed by timinginformation component 1006 and/or transmission component 1008 of FIG.10. The timing information may indicate information associated with asymbol and/or slot at a beginning of a frame of the downlinktransmission. For example, referring to FIGS. 4 and 5, the base station404, 504 or network indicates the timing information 402, 507 (e.g., acommon system timing) via unicast or broadcast signaling to UE 406, 506.The timing information 402, 507 may indicate information associated withone or more symbols and/or slots at the beginning of a downlinktransmission (e.g., frame 502 a). Referring to FIG. 8, the base station802 may send a downlink transmission 806 to the UE 804 at time t0, whichmay correspond to the start of a frame boundary from the perspective ofthe base station 802. The downlink transmission 806 may include timinginformation corresponding to the absolute time provided by thegrandmaster clock (e.g., timing information 507 in FIG. 5).

In one aspect of 904, the downlink transmission including the timinginformation is broadcast to a plurality of UEs. In another aspect of904, the downlink transmission including the timing information isunicast to the UE. For example, referring to FIG. 5, timing information507 received from the TSN (e.g., TSN 412) may be commonly broadcast tomultiple UEs, including the UE 506, and may include informationassociated with one or more symbols and/or one or more slots 510 at thebeginning of frames 502 a, 502 b. For example, the base station 504 maybroadcast the timing information 507 in a SIB at a 40 ns resolution. Insome other aspects, timing information 507 may be unicast to individualUEs 506 that need the timing information (for example, for individualapplications), and may indicate information associated with thebeginning of frames 502 a, 502 b. When unicast signaling is used, aseach UE has a respective local clock (e.g., local clock 418 in FIG. 4),potentially different timing information 507 with differentcompensations for the propagation delay 508 may be individually sent todifferent UEs, including the UE 506.

At 906, the base station receives an uplink transmission from the UEafter the downlink transmission. For example, 906 may be performed byreception component 1004 of FIG. 10. For example, referring to FIGS. 4and 5, after the UE 406, 506 receives the downlink transmission (e.g.,frame 502 b) including the timing information 402, 507 from the basestation 404, 504 after a propagation delay 508 from transmitted frame502 a, the base station 404, 504 receives an uplink transmission fromthe UE 406, 506. Referring to FIG. 8, after the UE 804 receives thedownlink transmission 806 at time t1, the UE 804 transmits an uplinktransmission 808 at time t2. The uplink transmission 808 may be, forexample, a SRS waveform (e.g., when the UE 804 is in connected mode) ora RACH waveform (e.g., when the UE 804 is in an idle mode). The basestation 802 subsequently receives the uplink transmission 808 at timet3.

At 908, the base station determines a RTT compensation associated withthe timing information based on a RTT between the downlink transmissionand the uplink transmission. For example, 908 may be performed by theRTT compensation determination component 1010 of FIG. 10. For example,referring to FIGS. 4 and 5, based on a RTT between the downlink anduplink transmissions, the base station 404, 504 may send a RTTcompensation for the UE 406, 506 associated with the timing information402, 507 determined from one or more of a TA within a TA command, atiming offset between a base station transmission and receptiontimelines, an estimated time difference between a base stationtransmission timing and a base station reception timing, and an actualtime difference between base station transmission and reception timingsand UE transmission and reception timings. For example, the base station404, 504 may transmit a TA 512 within a TA command as the RTTcompensation, and the UE may receive the TA 512 within a TA command asthe RTT compensation.

In one aspect of 908, the RTT compensation includes a TA associated withadjustment of the timing information transmitted to the UE. In oneaspect, the TA is transmitted in a TA command, and the TA command isassociated with a first TA granularity. For example, referring to FIGS.5, 6, the base station 504, 602 may determine the RTT compensation to bea TA 512, 603 within a TA command. The base station 504, 602 maydetermine a TA index value (e.g., a value of the 6-bit or 12-bit TAcommand illustrated in MAC-CE 700 of FIG. 7A or RAR 750 of FIG. 7B) forthe UE 506, 604 to identify the TA. The TA command may be associatedwith a TA granularity, which indicates a time (T_(s)) by which the TAindex value is multiplied in order to obtain the TA (e.g., TA 603 inFIG. 6). Examples of associated TA granularities are shown in Table 1above.

At 910, the base station indicates a second TA granularity to the UEthat is different from the first TA granularity based on an identity ofthe UE, where the identity of the UE indicates one of an IIOT UE or alegacy UE. Potentially, the second TA may be referred to as a “timingadvance refinement” and/or a “high precision timing advance.” In someaspects, the second TA may be transmitted to the UE without transmittingthe first TA. For example, the second TA may be used to indicate a finergranularity and/or higher precision than the first TA and so, in somecases, the first TA may be omitted. For example, 910 may be performed bythe granularity indication component 1012 of FIG. 10. The second TAgranularity may be finer than the first TA granularity. For example,referring to FIGS. 6 and 7A-7B, the base station 602 may configure aUE-specific TA granularity (e.g., a second TA granularity) differentthan the aforementioned TA granularities (e.g., a first TA granularity)shown, for instance, in Table 1. Thus, different TA granularities may beconfigured for different UEs based on a UE-reported identity of the UE(e.g., IIOT UEs or legacy UEs). For example, an IIOT UE may beconfigured with a finer (e.g., smaller) TA granularity associated with aSCS different than that of a legacy UE. The base station may indicatethe UE-specific TA granularities in downlink transmission, for example,by configuring MAC-CE 700 to have a new header or a larger size TAcommand which is transmitted to IIOT UEs separately from other TAcommands, or by transmitting MAC-CEs with different header values toconvey to UEs higher resolutions of TAs via different TA granularitieswithout increasing the size of the TA command.

In one aspect of 910, the second TA granularity may be preconfigured orindicated in a message separate from the TA command. For example,referring to FIGS. 7A and 7B, different TA granularities may be providedwithout changing the maximum size or header of the TA command 702, 752in MAC-CE 700 or RAR 750. For example, IIOT UEs may be configured with adifferent TA granularity than legacy UEs (e.g., 64 T_(s) or othergranularity smaller than those in Table 1) depending on the SCS forcommunication between the base station and UE. In another example,legacy UEs may request the base station or network to configure the UEswith a UE-specific TA granularity which may be different than other UEs.In some other aspects, a new MAC-CE with different size or header valuesthan MAC-CE 700 may be provided to UEs receiving TAs based on the secondset of TA granularities.

In another aspect of 910, the second TA granularity is indicated withinthe TA command. In various examples, one or more bits in the TA Command702 of MAC-CE 700 may be used to designate the TA as being based on afirst set of TA granularities (e.g., as shown for example in Table 1) orbased on a second set of finer TA granularities. In another example, oneof the values of the TAG ID 704 of MAC-CE 700 may be used to designatethe first or second set of TA granularities.

In certain aspects, a base station transmission timing for the downlinktransmission and a base station reception timing for the uplinktransmission are aligned within a guard period. In other aspects, theuplink transmission of the UE is received within a cyclic prefix of asubsequent downlink transmission. For example, referring to FIG. 6, thebase station transmission timeline 606 and the base station receptiontimeline 608 are aligned within a guard period when base station 602 andUE 604 communicate in a TDD mode. In other aspects, the uplinktransmissions from multiple UEs 604 may be received by the base station602 within the CP of a subsequent downlink transmission in either theTDD mode or a FDD mode.

In another aspect of 908, the RTT compensation may indicated as a TAbased on a timing offset between a base station transmission timing anda base station reception timing. The timing offset is transmitted to theUE in a separate message from the timing information. For example,referring to FIG. 6, the base station may determine the RTT compensationto be a timing offset 614 between base station transmission andreception timelines 606, 608. In various aspects, the base station mayindicate the timing offset 614 to the UE via a separate message from thetiming information, rather than applying the timing offset 614 to thebroadcasted timing information advertised by the base station.

In a further aspect of 908, the RTT compensation may be an estimatedtime difference between a base station transmission timing for thedownlink transmission and a base station reception timing for the uplinktransmission. The estimated time difference may be transmitted to the UEin a separate message from a TA command. For example, referring to FIG.8, the base station may determine the RTT compensation to be anestimated time difference (A) between a base station transmission timing(t0) for a downlink transmission 806 and a base station reception timing(t3) for an uplink transmission 808. The base station may estimate thevalue A by calculating the difference between t3 and t0, and may sendthe value A in the downlink transmission 806. The message including thevalue A may be, for example, a layer 2 MAC message or a layer 3 RRCmessage transmitted by the base station to the UE separate from a TAcommand.

In certain aspects where the RTT compensation is separate from the TAcommand, the TA command may associated with a first TA granularity, andthe RTT compensation may indicate a second TA granularity different thanthe first TA granularity. For example, referring to FIG. 8, the basestation 802 or network may indicate, in a separate message from the TAcommand, the value A as the RTT compensation for UE 804 to use fortiming synchronization. In contrast to TA command 702 or 752 (see FIG.7), which may be limited in size to a small number of bits andassociated with a TA granularity such as those in Table 1 above, themessage including the value A may not be so limited and be associatedwith finer TA granularities, therefore ranging in the tens ofnanoseconds, for example. Thus, the value A has higher granularity orprecision for timing adjustment than the TA command, which may beconstrained in size to the larger, microsecond range as described above.

In an additional aspect of 908, the determined RTT compensation may bean actual time difference between the base station time difference andthe UE time difference. To make this determination, at 912, the basestation receives a UE time difference between a UE reception timing forthe downlink transmission and a UE transmission timing for the uplinktransmission, and at 914, the base station determines a base stationtime difference between a base station transmission timing for thedownlink transmission and a base station reception timing for the uplinktransmission. For example, 912 may be performed by the receptioncomponent 1004, and 914 may be performed by the base station timedifference determination component 1014. For example, referring to FIG.8, after the UE receives at time t1 the downlink transmission 806 sentat time t0, the UE 804 may transmit at time t2 to the base station 802the value B (the UE time difference between t2 and t1) in uplinktransmission 808. Once the base station receives the value B at time t3,the base station may obtain the RTT and thus the propagation delay bycalculating the actual value A (the base station time difference betweent3 and t0) and subtracting the UE-indicated value B (t2−t1). The basestation may thus determine the RTT compensation to be an actual timedifference (A−B) between the base station transmission timing (t0) andbase station reception timing (t3), and the UE transmission timing (t2)and the UE reception timing (a).

At 916, the base station adjusts the timing information based on the RTTcompensation. For example, 916 may be performed by the base stationtiming adjustment component 1016 of FIG. 10. For example, referring toFIG. 8, if the downlink transmission 806 was unicast to UE 804, the basestation 802 may adjust the timing information with the RTT compensationand send the adjusted timing information to the UE.

At 918, the base station transmits the RTT compensation to the UE. Forexample, 918 may be performed by the transmission component 1008 of FIG.10. The RTT compensation allows RTT to occur within at most 1microsecond of the downlink transmission. For example, referring toFIGS. 4-8, the base station 404 may send a RTT compensation to the UE406. The timing information 402, 507 may be transmitted with the RTTcompensation. In one aspect, the RTT compensation may be a TA 512 withina TA command. The RTT compensation may be sent, for example, at time t1in the base station transmission timeline 606. In another aspect,referring to FIG. 6, the RTT compensation may be the timing offset 614,and the base station may indicate the timing offset 614 to the UE via aseparate message from the timing information. The separate message maybe a PLY message, a MAC message, or a RRC message. In a further aspect,referring to FIG. 8, the RTT compensation may be the estimated value A,and the base station 802 or network may indicate, in a separate messagefrom the TA command, the value A as the RTT compensation for UE 804 touse for timing synchronization. The separate message may be a PLYmessage, a MAC message, or a RRC message. In an additional aspect,referring to FIG. 8, the RTT compensation may be the value (A−B), andthe base station 802 or network may provide the RTT compensation (e.g.,the difference between the values of A and B) to the UE 804 based onwhether the downlink transmission 806 including the timing information(e.g., the grandmaster clock time) was broadcast or unicast to the UE804. In this way, base stations may deliver timing information to UEs inoutdoor scenarios while taking into account RTT compensation to meet the≤1 μs synchronization accuracy parameter of IEEE1588v2/Precision TimeProtocol.

In certain aspects of 918, when the downlink transmission is broadcast,the RTT compensation is transmitted to a plurality of UEs. In otheraspects, when the downlink transmission is unicast, the timinginformation is adjusted based on the RTT compensation, and the adjustedtiming information is transmitted to the UE. For example, referring toFIG. 8, the base station 802 or network may provide the RTT compensation(e.g., the difference between the values of A and B) to the UE 804 basedon whether the downlink transmission 806 including the timinginformation (e.g., the grandmaster clock time) was broadcast or unicastto the UE 804. In one aspect, if the downlink transmission 806 wasbroadcast to UE 804, the base station 802 may provide the RTTcompensation to the UE for the UE to adjust its local clock tosynchronize the timing information. For example, the RTT compensationmay be broadcast to a plurality of UEs. In another aspect, if thedownlink transmission 806 was unicast to UE 804, the base station 802may either provide the RTT compensation to the UE as discussed above, oradjust the timing information with the RTT compensation and send theadjusted timing information to the UE.

FIG. 10 is a conceptual data flow diagram 1000 illustrating the dataflow between different means/components in an example apparatus 1002.The apparatus may be a base station (e.g., the base station 102, 310,404, 504, 602, 802) in communication with a UE 1050 (e.g., the UE 104,350, 406, 506, 604, 804) and a TSN (e.g., TSN system 412).

The apparatus 1002 includes a reception component 1004 that receivestiming information from a TSN, e.g., as described in connection with 902from FIG. 9. The reception component 1004 also receives an uplinktransmission from the UE 1050 after the downlink transmission, e.g., asdescribed in connection with 906 from FIG. 9. The reception component1004 also receives a UE time difference between a UE reception timingfor the downlink transmission and a UE transmission timing for theuplink transmission, e.g., as described in connection with 912 from FIG.9. The reception component 1004 further receives an identity reported bythe UE, e.g., as described in connection with 910 from FIG. 9.

The apparatus 1002 includes a timing information component 1006 thatreceives the timing information from a TSN system 1060 (e.g., TSN 412)via the reception component 1004, e.g., as described in connection with902 from FIG. 9. The global clock 1070 of the base station may beupdated with the timing information. The timing information component1006 also sends a downlink transmission including the timing informationto UE 1050 via a transmission component 1008, e.g., as described inconnection with 904 from FIG. 9. While FIG. 10 illustrates the globalclock 1070 as part of the timing information component 1006, they may beseparate components.

The apparatus 1002 includes a RTT compensation determination component1010 that determines a RTT compensation associated with the timinginformation based on a RTT between the downlink transmission and theuplink transmission, e.g., as described in connection with 908 from FIG.9. The RTT compensation determination component 1010 includes agranularity indication component 1012, which indicates a second TAgranularity to the UE different from the first TA granularity based onthe identity of the UE received via the reception component 1004, e.g.,as described in connection with 910 from FIG. 9. The RTT compensationdetermination component 1010 further includes a base station timedifference determination component 1014, which determines a base stationtime difference between a base station transmission timing for thedownlink transmission and a base station reception timing for the uplinktransmission, e.g., as described in connection with 914 from FIG. 9. TheRTT compensation determination component 1010 further transmits the RTTcompensation to the UE via the transmission component 1008, e.g., asdescribed in connection with 918 of FIG. 9.

The apparatus 1002 additionally includes a base station timingadjustment component 1016 that adjusts the timing information based onthe RTT compensation received from the RTT compensation determinationcomponent 1010 and the timing information received from the timinginformation component 1006, e.g., as described in connection with 916from FIG. 9. The base station timing adjustment component 1016 sends theadjusted timing information to the UE 1050, via the transmissioncomponent 1008.

The transmission component 1008 of the apparatus 1002 sends to UE 1050downlink transmissions including timing information received from thetiming information component 1006, RTT compensation received from theRTT compensation determination component 1010, and adjusted timinginformation received from the base station timing adjustment component1016.

The apparatus 1002 may include additional components that perform eachof the blocks of the algorithm in the aforementioned flowchart of FIG.9. As such, each block in the aforementioned flowchart of FIG. 9 may beperformed by a component and the apparatus may include one or more ofthose components. The components may be one or more hardware componentsspecifically configured to carry out the stated processes/algorithm,implemented by a processor configured to perform the statedprocesses/algorithm, stored within a computer-readable medium forimplementation by a processor, or some combination thereof.

FIG. 11 is a diagram 1100 illustrating an example of a hardwareimplementation for an apparatus 1002′ employing a processing system1114. The processing system 1114 may be implemented with a busarchitecture, represented generally by the bus 1124. The bus 1124 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 1114 and the overalldesign constraints. The bus 1124 links together various circuitsincluding one or more processors and/or hardware components, representedby the processor 1104, the components 1004, 1006, 1008, 1010, 1012,1014, 1016, and the computer-readable medium/memory 1106. The bus 1124may also link various other circuits such as timing sources,peripherals, voltage regulators, and power management circuits, whichare well known in the art, and therefore, will not be described anyfurther.

The processing system 1114 may be coupled to a transceiver 1110. Thetransceiver 1110 is coupled to one or more antennas 1120. Thetransceiver 1110 provides a means for communicating with various otherapparatus over a transmission medium. The transceiver 1110 receives asignal from the one or more antennas 1120, extracts information from thereceived signal, and provides the extracted information to theprocessing system 1114, specifically the reception component 1004. Inaddition, the transceiver 1110 receives information from the processingsystem 1114, specifically the transmission component 1008, and based onthe received information, generates a signal to be applied to the one ormore antennas 1120. The processing system 1114 includes a processor 1104coupled to a computer-readable medium/memory 1106. The processor 1104 isresponsible for general processing, including the execution of softwarestored on the computer-readable medium/memory 1106. The software, whenexecuted by the processor 1104, causes the processing system 1114 toperform the various functions described supra for any particularapparatus. The computer-readable medium/memory 1106 may also be used forstoring data that is manipulated by the processor 1104 when executingsoftware. The processing system 1114 further includes at least one ofthe components 1004, 1006, 1008, 1010, 1012, 1014, 1016. The componentsmay be software components running in the processor 1104,resident/stored in the computer readable medium/memory 1106, one or morehardware components coupled to the processor 1104, or some combinationthereof. The processing system 1114 may be a component of the basestation 310 and may include the memory 376 and/or at least one of the TXprocessor 316, the RX processor 370, and the controller/processor 375.In some other aspects, the processing system 1114 may be the entire basestation (e.g., see 310 of FIG. 3).

In one configuration, the apparatus 1002/1002′ for wirelesscommunication includes means for sending a downlink transmissionincluding timing information to a UE; means for receiving an uplinktransmission from the UE after the downlink transmission; means fordetermining a RTT compensation associated with the timing informationbased on a RTT between the downlink transmission and the uplinktransmission; and means for transmitting the RTT compensation to the UE.The apparatus 1002/1002′ may further include means for receiving thetiming information from a TSN; means for adjusting the timinginformation based on the RTT compensation; and means for indicating asecond TA granularity to the UE different from the first TA granularitybased on an identity of the UE, wherein the identity of the UE indicatesone of an IIOT UE or a legacy UE. The apparatus 1002/1002′ mayadditionally include means for receiving a UE time difference between aUE reception timing for the downlink transmission and a UE transmissiontiming for the uplink transmission; and means for determining a basestation time difference between a base station transmission timing forthe downlink transmission and a base station reception timing for theuplink transmission.

The aforementioned means may be one or more of the aforementionedcomponents of the apparatus 1002 and/or the processing system 1114 ofthe apparatus 1002′ configured to perform the functions recited by theaforementioned means. As described supra, the processing system 1114 mayinclude the TX Processor 316, the RX Processor 370, and thecontroller/processor 375. As such, in one configuration, theaforementioned means may be the TX Processor 316, the RX Processor 370,and the controller/processor 375 configured to perform the functionsrecited by the aforementioned means.

FIG. 12 is a flowchart 1200 of a method of wireless communication. Themethod may be performed by a UE (e.g., the UE 104, 350, 406, 506, 604,804; the apparatus 1302/1302′; the processing system 1414, which mayinclude the memory 360 and which may be the entire UE 104, 350, 406,506, 604, 804 or a component of the UE 104, 350, 406, 506, 604, 804,such as the TX processor 368, the RX processor 356, and/or thecontroller/processor 359). Optional aspects are illustrated in dashedlines. The method allows a UE to obtain RTT compensation from a basestation to use in adjusting their individual or local time clocks,thereby allowing UEs to synchronize at a high precision with the timeclock of the base station. The present disclosure further allows UEs tobe configured with different resolutions or granularities in timingcorrection so that certain UEs can achieve high precision timingcorrection while other UEs can adjust their time clocks with lessprecision.

At 1202, the UE receives a downlink transmission including timinginformation from a base station. For example, 1202 may be performed bythe reception component 1304 of FIG. 13. The timing information mayindicate information associated with a beginning of a frame of thedownlink transmission. For example, referring to FIGS. 4 and 5, the UE406, 506 receives a downlink transmission (e.g., frame 502 b) includingthe timing information 402, 507 from the base station after apropagation delay 508 from transmitted frame 502 a. The timinginformation 402, 507 may be associated with one or more symbols and/orslots at the beginning of a downlink transmission (e.g., frame 502 aand/or frame 502 b). Moreover, referring to FIG. 8, the UE 804 mayreceive a downlink transmission 806 at time t1, corresponding to thestart of a frame boundary from the perspective of the UE. The downlinktransmission 806 may include timing information corresponding to theabsolute time provided by the grandmaster clock (e.g., timinginformation 507 in FIG. 5).

In one aspect of 1202, the downlink transmission including the timinginformation is received via broadcast. In another aspect of 1202, thedownlink transmission including the timing information is received viaunicast. For example, referring to FIG. 5, timing information 507received from the TSN (e.g., TSN 412) may be commonly broadcast tomultiple UEs 506, and the timing information 507 may refer to one ormore symbols and/or one or more slots 510 at the beginning of frames 502a, 502 b. In some other aspects, timing information 507 may be unicastto individual UEs 506 that should receive the timing information (forexample, for individual applications), and/or may refer to the beginningof frames 502 a, 502 b. When unicast signaling is used, as each UE hastheir own local clock (e.g., local clock 418 in FIG. 4), potentiallydifferent timing information 507 with different compensations forpropagation delay 508 may be individually received by different UEs 506.

At 1204, the UE sends an uplink transmission to the base station afterthe downlink transmission. For example, 1204 may be performed bytransmission component 1314 of FIG. 13. For example, referring to FIGS.4 and 5, after the UE 406, 506 receives the downlink transmission (e.g.,frame 502 b) including the timing information 402, 507 from the basestation, the UE may subsequently send an uplink transmission.

In certain aspects, a base station transmission timing for the downlinktransmission and a base station reception timing for the uplinktransmission are aligned within a guard period. In other aspects, theuplink transmission is transmitted to the base station within a cyclicprefix of a subsequent downlink transmission. For example, referring toFIG. 6, the base station transmission timeline 606 and the base stationreception timeline 608 are aligned within a guard period when basestation 602 and UE 604 communicate in a TDD mode. In other aspects, theuplink transmissions from multiple UEs 604 may be received by the basestation 602 within the CP of a subsequent downlink transmission ineither the TDD mode or a FDD mode.

At 1206, the UE obtains a RTT compensation for the timing informationbased on a RTT between the downlink transmission and the uplinktransmission. For example, 1206 may be performed by the RTT compensationcomponent 1306. The RTT compensation allows RTT to occur within at most1 microsecond of the downlink transmission. For example, referring toFIGS. 4 and 5, based on a RTT between the downlink and uplinktransmissions, the UE 406 may obtain from base station 404 a RTTcompensation for the UE 406 associated with the timing information 402,507. The RTT compensation may be one or more of a TA within a TAcommand, a timing offset between a base station transmission andreception timelines, an estimated time difference between a base stationtransmission timing and a base station reception timing, and an actualtime difference between base station transmission and reception timingsand UE transmission and reception timings. For example, the base stationmay transmit as the RTT compensation, and the UE may receive as the RTTcompensation, a TA 512 within a TA command. In this way, base stationsmay deliver timing information to UEs in outdoor scenarios while takinginto account RTT compensation to meet the ≤1 μs synchronization accuracyparameter of IEEE1588v2/Precision Time Protocol.

In one aspect of 1206, the RTT compensation may be a TA for adjustingthe timing information received by the UE. In one aspect, the TA isreceived in a TA command, and the TA command is associated with a firstTA granularity. For example, referring to FIGS. 5, 6, 7A and 7B, the UEmay receive the RTT compensation (e.g., a TA 512) within a TA command.The TA is based on a TA index value (e.g., a value of the 6-bit or12-bit TA command illustrated in FIG. 7A or 7B) and a TA granularity,which indicates a time (T_(s)) by which the TA index value is multipliedin order to obtain the TA. Examples of associated TA granularities areshown in Table 1 above. For example, when the UE 604 receives thedownlink transmission including the timing information and a TA 603 attime t2, assuming a TA granularity associated with a 15 kHz SCS and a TAindex value of 2, the UE 604 may advance its UE transmission timeline610 by approximately 1 μs or 1000 ns with respect to the global clock ofthe base station 602.

At 1207, the UE reports an identity of the UE to the base station, wherethe identity of the UE indicates one of an IIOT UE or a legacy UE. Forexample, 1207 may be performed by the identity report component 1318 ofFIG. 13. For example, referring to FIGS. 6 and 7A-7B, the UE (e.g., UE604) may report its identity as either an IIOT UE or a legacy UE to thebase station (e.g., base station 602) or another network node (forexample, during a SRS, RACH, or other uplink transmission). Depending onthe reported identity of the UE, the base station may configure orindicate UE-specific TA granularities. For example, if the UE transmitsa message to the base station including an identification as a legacyUE, the base station may configure the UE with a TA granularity inaccordance with Table 1. In another example, if the UE transmits amessage to the base station including an identification as an IIOT UE,the base station may indicate to the UE a UE-specific TA granularitywhich is finer than those indicated above in Table 1. In other examples,the base station may indicate identical or larger TA granularities toIIOT UEs compared to legacy UEs.

At 1208, the UE receives a second TA granularity different from thefirst TA granularity based on an identity of the UE, where the identityof the UE indicates one of an IIOT UE or a legacy UE. Potentially, thesecond TA may be referred to as a “timing advance refinement” and/or a“high precision timing advance.” In some aspects, the second TA may bereceived without receiving the first TA. For example, the second TA maybe used to indicate a finer granularity and/or higher precision than thefirst TA and so, in some cases, the first TA may be omitted. Forexample, 1208 may be performed by the granularity reception component1308 of FIG. 13. The second TA granularity is finer than the first TAgranularity. For example, referring to FIGS. 6 and 7A-7B, the UE 604 maybe configured with a UE-specific TA granularity (e.g., a second TAgranularity) different than the aforementioned TA granularities (e.g., afirst TA granularity) shown, for instance, in Table 1. Thus, differentTA granularities may be configured for different UEs based on theidentity reported by the UE at 1207 (e.g., IIOT UEs or legacy UEs). Forexample, an IIOT UE may be configured with a finer (e.g., smaller) TAgranularity associated with a SCS than that of a legacy UE. The UE mayreceive a UE-specific TA granularity in downlink transmission, throughfor example, a MAC-CE 700 reconfigured to have a new header or a largersize TA command which is received by IIOT UEs separately from other TAcommands, or by receiving MAC-CEs with different header values conveyinghigher resolutions of TAs via different TA granularities withoutincreasing the size of the TA command.

In one aspect of 1208, the second TA granularity is preconfigured orreceived in a separate message from the TA command. For example,referring to FIGS. 7A and 7B, different TA granularities may beconfigured or received without changing the maximum size or header ofthe TA command 702, 752 in MAC-CE 700 or RAR 750. For example, IIOT UEsmay be configured with a different TA granularity than legacy UEs (e.g.,64 T_(s) or other granularity smaller than those in Table 1) dependingon the SCS for communication between the base station and UE. In anotherexample, legacy UEs may request the base station or network to configurethe UEs with a UE-specific TA granularity which may be different thanother UEs. In some other aspects, a new MAC-CE with different size orheader values than MAC-CE 700 may be received by UEs configured toreceive TAs based on the second set of TA granularities.

In another aspect of 1208, the second TA granularity is received withinthe TA command. In various examples, one or more bits in the TA Command702 of MAC-CE 700 may be used to designate the TA as being based on afirst set of TA granularities (e.g., as shown for example in Table 1) orbased on a second set of finer TA granularities. In another example, oneof the values of the TAG ID 704 of MAC-CE 700 may be used to designatethe first or second set of TA granularities.

In a further aspect of 1206, the RTT compensation may be a TA based on atiming offset between a base station transmission timing for thedownlink transmission and a base station reception timing for the uplinktransmission. The timing offset is received in a separate message fromthe timing information. For example, referring to FIG. 6, the TA 603received and applied by the UE may be based on the timing offset 614(e.g., gNBRxOffset) between the base station transmission timeline 606and base station reception timeline 608. In various aspects, the UE mayreceive the timing offset 614 from the base station via a separatemessage from the timing information, rather than receiving the timingoffset 614 already applied to the broadcasted timing informationadvertised by the base station. The separate message may be a PLYmessage, a MAC message, or a RRC message received from the base station.

In another aspect of 1206, the RTT compensation may be an estimated timedifference between a base station transmission timing for the downlinktransmission and a base station reception timing for the uplinktransmission. The estimated time difference may be received in aseparate message from a TA command. For example, referring to FIG. 8,the value A represents the base station time difference 810 between t3(the base station reception timing for an uplink transmission 808) andt0 (the base station transmission timing for a downlink transmission806). In one aspect, the base station 802 estimates the value A bycalculating the difference between t3 and t0, and the UE 804 receivesthe value A from the base station in a message. The message includingthe value A may be, for example, a PLY message, a layer 2 MAC message ora layer 3 RRC message transmitted by the base station to the UE separatefrom a TA command.

In certain aspects where the RTT compensation is separate from the TAcommand, the TA command is associated with a first TA granularity, andthe RTT compensation indicates a second TA granularity different thanthe first TA granularity. For example, referring to FIG. 8, the UE 804may receive from the base station 802 or network, in a separate messagefrom the TA command, the value A as the RTT compensation for UE 804 touse for timing synchronization. In contrast to TA command 702 or 752(see FIG. 7), which may be limited in size to a small number of bits andassociated with a TA granularity such as those in Table 1 above, themessage including the value A may not be so limited and be associatedwith finer TA granularities, therefore ranging in the tens ofnanoseconds, for example. Thus, the value A has higher granularity orprecision for timing adjustment than the TA command, which may beconstrained in size to the larger, microsecond range as described above.

In an additional aspect of 906, the RTT compensation may be an actualtime difference between a base station time difference and a UE timedifference, where the base station time difference is the differencebetween a base station transmission timing for an downlink transmissionand a base station reception timing for an uplink transmission, andwhere the UE time difference is the difference between a UE transmissiontiming for the uplink transmission and a UE reception timing for thedownlink transmission. To obtain the actual time difference, at 1210,the UE determines a UE time difference between a UE reception timing forthe downlink transmission and a UE transmission timing for the uplinktransmission, and at 1212, the UE indicates the UE time difference tothe base station. For example, 1210 may be performed by the UE timedifference determination component 1310 of FIG. 13, and 1212 may beperformed by the indication component 1312 of FIG. 13. For example,referring to FIG. 8, after the UE 804 receives at time t1 the downlinktransmission 806 sent at time t0, and prior to transmitting the uplinktransmission 808 at time t2 to the base station 802, the UE determinesthe value B (the UE time difference between t2 and t1). The UE 804 maythen indicate at time t2 the value B in uplink transmission 808 to thebase station 802. Once the base station receives the value B at time t3,the base station may obtain the RTT and thus the propagation delay bycalculating the actual value A (the base station time difference betweent3 and t0) and subtracting the UE-indicated value B (t2−t1). The actualtime difference (A−B) may thus be determined between the base stationtransmission timing (t0) and base station reception timing (t3), and theUE transmission timing (t2) and the UE reception timing (a).

In certain aspects of 1206, when the downlink transmission is broadcast,the RTT compensation is received via broadcast. In other aspects, whenthe downlink transmission is unicast, adjusted timing information basedon the RTT compensation is received from the base station. For example,referring to FIG. 8, the UE 804 may receive the RTT compensation (e.g.,the difference between the values of A and B) from the base station 802or network based on whether the downlink transmission 806 including thetiming information (e.g., the grandmaster clock time) was broadcast orunicast to the UE 804. In one aspect, if the downlink transmission 806was broadcast to UE 804, the UE 804 may receive the RTT compensationfrom the base station 802 for the UE to adjust its local clock tosynchronize the timing information. In another aspect, if the downlinktransmission 806 was unicast to UE 804, the UE may either receive theRTT compensation from the base station 802 as discussed above, or the UEmay receive timing information already adjusted with the RTTcompensation from the base station.

At 1214, the UE adjusts the timing information based on the RTTcompensation, where the timing information is delivered to an upperlayer of the UE. The timing information delivered to the upper layer isbased on a UE reception timing for the downlink transmission and the RTTcompensation. For example, 1214 may be performed by the UE timingadjustment component 1316 of FIG. 13. For example, referring to FIGS. 4,5, and 6, after receiving the TA command with the RTT compensation(e.g., TA 512), the UE 406, 506 may adjust its local clock 418 with theTA 512 and deliver the adjusted time to the upper layers 514 of the UE406, 506 (e.g., layer 2/layer 3). The time delivered may also be basedon timing offset 614. For example, the UE may deliver an adjusted timeto the upper layers 514 based on the following formula after receiving abroadcast timing information 402, 507:Time Delivered to Upper Layer=Broadcasted Time+“Applied TAAdvance”/2−gNBRxOffset, where:Broadcasted Time is the UE reception timing of the downlink transmissionindicating the timing information 402, 507 after propagation delay 508;Applied TA Advance is the TA 512 indicated in the TA command; andgNBRxOffset is the timing offset 614 between the base stationtransmission timeline 606 and base station reception timeline 608.

At 1216, the UE adjusts the timing information based on the RTTcompensation and a time difference between a UE reception timing for thedownlink transmission and a UE transmission timing for the uplinktransmission. For example, 1216 may be performed by the UE timingadjustment component 1316 of FIG. 13. For example, referring to FIG. 8,once the UE 804 obtains the timing information with the RTT compensation(e.g., the value A), the UE 804 may determine to adjust the timinginformation based on the propagation delay derived from the RTTcompensation and the value B (the UE time difference 812 between UEtransmission timing t2 and UE reception timing t1). For instance, the UEmay calculate the RTT by subtracting the value B from the received valueA from the base station. The UE may then divide the RTT by two to obtainthe one-way propagation delay, which the UE may use to adjust the timinginformation received from the base station to synchronize its localclock with the global clock.

FIG. 13 is a conceptual data flow diagram 1300 illustrating the dataflow between different means/components in an example apparatus 1302.The apparatus may be a UE (e.g., UE 104, 350, 406, 506, 604, 804) incommunication with a base station (e.g., the base station 102, 310, 404,504, 602, 802).

The apparatus 1302 includes a reception component 1304 that receives adownlink transmission including timing information from a base station,e.g., as described in connection with 1202 from FIG. 12. The timinginformation updates a local clock 1360 of the apparatus 1302.

The apparatus 1302 includes a RTT compensation component 1306 thatobtains a RTT compensation for the timing information based on a RTTbetween the downlink transmission and the uplink transmission, e.g., asdescribed in connection with 1206 from FIG. 12. The RTT compensationcomponent 1306 includes a granularity reception component 1308 whichreceives, via the reception component 1304, a second TA granularitydifferent from the first TA granularity based on an identity of the UE,e.g., as described in connection with 1208 from FIG. 12.

The apparatus 1302 also includes a UE time difference determinationcomponent 1310 that determines a UE time difference between a UEreception timing for the downlink transmission and a UE transmissiontiming for the uplink transmission, e.g., as described in connectionwith 1210 from FIG. 12. The apparatus further includes an indicationcomponent 1312 that indicates the UE time difference to the base stationvia a transmission component 1314 of the apparatus 1302, e.g., asdescribed in connection with 1212 from FIG. 12.

The apparatus 1302 additionally includes a UE timing adjustmentcomponent 1316 that adjusts the timing information based on the RTTcompensation, the timing information being delivered to an upper layerof the UE, e.g., as described in connection with 1214 from FIG. 12. TheUE timing adjustment component 1316 also adjusts the timing informationbased on the RTT compensation and a time difference between a UEreception timing for the downlink transmission and a UE transmissiontiming for the uplink transmission, e.g., as described in connectionwith 1216 from FIG. 12.

The transmission component 1314 sends an uplink transmission to the basestation 1350 after the downlink transmission received via the receptioncomponent 1304. The transmission component 1314 also sends the UE timedifference received from the indication component 1312. The transmissioncomponent 1314 further sends to base station 1350 an identity of the UE(e.g., an IIOT UE or a legacy UE) received from an identity reportcomponent 1318 of apparatus 1302.

The apparatus may include additional components that perform each of theblocks of the algorithm in the aforementioned flowchart of FIG. 12. Assuch, each block in the aforementioned flowchart of FIG. 12 may beperformed by a component and the apparatus may include one or more ofthose components. The components may be one or more hardware componentsspecifically configured to carry out the stated processes/algorithm,implemented by a processor configured to perform the statedprocesses/algorithm, stored within a computer-readable medium forimplementation by a processor, or some combination thereof.

FIG. 14 is a diagram 1400 illustrating an example of a hardwareimplementation for an apparatus 1302′ employing a processing system1414. The processing system 1414 may be implemented with a busarchitecture, represented generally by the bus 1424. The bus 1424 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 1414 and the overalldesign constraints. The bus 1424 links together various circuitsincluding one or more processors and/or hardware components, representedby the processor 1404, the components 1304, 1306, 1308, 1310, 1312,1314, 1316, 1318, and the computer-readable medium/memory 1406. The bus1424 may also link various other circuits such as timing sources,peripherals, voltage regulators, and power management circuits, whichare well known in the art, and therefore, will not be described anyfurther.

The processing system 1414 may be coupled to a transceiver 1410. Thetransceiver 1410 is coupled to one or more antennas 1420. Thetransceiver 1410 provides a means for communicating with various otherapparatus over a transmission medium. The transceiver 1410 receives asignal from the one or more antennas 1420, extracts information from thereceived signal, and provides the extracted information to theprocessing system 1414, specifically the reception component 1304. Inaddition, the transceiver 1410 receives information from the processingsystem 1414, specifically the transmission component 1314, and based onthe received information, generates a signal to be applied to the one ormore antennas 1420. The processing system 1414 includes a processor 1404coupled to a computer-readable medium/memory 1406. The processor 1404 isresponsible for general processing, including the execution of softwarestored on the computer-readable medium/memory 1406. The software, whenexecuted by the processor 1404, causes the processing system 1414 toperform the various functions described supra for any particularapparatus. The computer-readable medium/memory 1406 may also be used forstoring data that is manipulated by the processor 1404 when executingsoftware. The processing system 1414 further includes at least one ofthe components 1304, 1306, 1308, 1310, 1312, 1314, 1316, 1318. Thecomponents may be software components running in the processor 1404,resident/stored in the computer readable medium/memory 1406, one or morehardware components coupled to the processor 1404, or some combinationthereof. The processing system 1414 may be a component of the UE 350 andmay include the memory 360 and/or at least one of the TX processor 368,the RX processor 356, and the controller/processor 359. In some otheraspects, the processing system 1414 may be the entire UE (e.g., see 350of FIG. 3).

In one configuration, the apparatus 1302/1302′ for wirelesscommunication includes means for receiving a downlink transmissionincluding timing information from a base station; means for sending anuplink transmission to the base station after the downlink transmission;and means for obtaining a RTT compensation for the timing informationbased on a RTT between the downlink transmission and the uplinktransmission. The apparatus 1302/1302′ may also include means foradjusting the timing information based on the RTT compensation, wherethe timing information is delivered to an upper layer of the apparatus1302/1302′, and means for adjusting the timing information based on theRTT compensation and a time difference between a UE reception timing forthe downlink transmission and a UE transmission timing for the uplinktransmission. The apparatus 1302/1302′ may further include means forreceiving a second TA granularity different from the first timingadvance granularity based on an identity of the apparatus 1302/1302′,wherein the identity of the apparatus 1302/1302′ indicates one of anIIOT UE or a legacy UE. The apparatus 1302/1302′ may additionallyinclude means for determining a UE time difference between a UEreception timing for the downlink transmission and a UE transmissiontiming for the uplink transmission; and means for indicating the UE timedifference to the base station, wherein the RTT compensation indicatesan actual time difference between a base station time difference and theUE time difference, the base station time difference being thedifference between a base station transmission timing for the downlinktransmission and a base station reception timing for the uplinktransmission.

The aforementioned means may be one or more of the aforementionedcomponents of the apparatus 1302 and/or the processing system 1414 ofthe apparatus 1302′ configured to perform the functions recited by theaforementioned means. As described supra, the processing system 1414 mayinclude the TX Processor 368, the RX Processor 356, and thecontroller/processor 359. As such, in one configuration, theaforementioned means may be the TX Processor 368, the RX Processor 356,and the controller/processor 359 configured to perform the functionsrecited by the aforementioned means.

The present disclosure thus allows a base station to indicate RTTcompensation for UEs to use in adjusting their individual or local timeclocks, thereby allowing UEs to synchronize at a high precision with thetime clock of the base station. The present disclosure further allowsUEs to be configured with different resolutions or granularities intiming correction so that certain UEs can achieve high precision timingcorrection while other UEs can adjust their time clocks with lessprecision. In this way, base stations may deliver timing information toUEs in outdoor scenarios while taking into account RTT compensation tomeet the ≤1 μs synchronization accuracy parameter ofIEEE1588v2/Precision Time Protocol. Moreover, certain UEs (e.g., IIOTUEs) may obtain higher precision for timing correction while other UEs(e.g., non-IIOT UEs and/or legacy UEs may observe other, less precisetiming synchronization parameters).

It is understood that the specific order or hierarchy of blocks in theprocesses/flowcharts disclosed is an illustration of example approaches.Based upon design preferences, it is understood that the specific orderor hierarchy of blocks in the processes/flowcharts may be rearranged.Further, some blocks may be combined or omitted. The accompanying methodclaims present elements of the various blocks in a sample order, and arenot meant to be limited to the specific order or hierarchy presented.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” The word “exemplary” is used hereinto mean “serving as an example, instance, or illustration.” Any aspectdescribed herein as “exemplary” is not necessarily to be construed aspreferred or advantageous over other aspects. Unless specifically statedotherwise, the term “some” refers to one or more. Combinations such as“at least one of A, B, or C,” “one or more of A, B, or C,” “at least oneof A, B, and C,” “one or more of A, B, and C,” and “A, B, C, or anycombination thereof” include any combination of A, B, and/or C, and mayinclude multiples of A, multiples of B, or multiples of C. Specifically,combinations such as “at least one of A, B, or C,” “one or more of A, B,or C,” “at least one of A, B, and C,” “one or more of A, B, and C,” and“A, B, C, or any combination thereof” may be A only, B only, C only, Aand B, A and C, B and C, or A and B and C, where any such combinationsmay contain one or more member or members of A, B, or C. All structuraland functional equivalents to the elements of the various aspectsdescribed throughout this disclosure that are known or later come to beknown to those of ordinary skill in the art are expressly incorporatedherein by reference and are intended to be encompassed by the claims.Moreover, nothing disclosed herein is intended to be dedicated to thepublic regardless of whether such disclosure is explicitly recited inthe claims. The words “module,” “mechanism,” “element,” “device,” andthe like may not be a substitute for the word “means.” As such, no claimelement is to be construed as a means plus function unless the elementis expressly recited using the phrase “means for.”

What is claimed is:
 1. A method of wireless communication by a basestation, comprising: sending timing information to a user equipment(UE), the timing information configuring a local clock at the UE basedon a grandmaster clock of a time-sensitive network (TSN); receiving anuplink transmission from the UE after a downlink transmission to the UE;determining a round-trip time (RTT) compensation associated withadjusting the timing information based on a RTT that is measured usingthe downlink transmission and the uplink transmission; and transmittingthe RTT compensation to the UE.
 2. The method of claim 1, furthercomprising: receiving information indicating the grandmaster clock ofthe TSN.
 3. The method of claim 1, wherein the RTT is measured from abeginning of a frame of the downlink transmission.
 4. The method ofclaim 1, wherein the timing information is one of broadcast to aplurality of UEs or is unicast to the UE.
 5. The method of claim 1,further comprising: adjusting the timing information based on the RTTcompensation.
 6. The method of claim 1, wherein the RTT compensationcomprises a timing advance associated with adjustment of the timinginformation transmitted to the UE.
 7. The method of claim 6, wherein abase station transmission timing for the downlink transmission and abase station reception timing for the uplink transmission are alignedwithin a guard period.
 8. The method of claim 6, wherein the uplinktransmission of the UE is received within a cyclic prefix of asubsequent downlink transmission.
 9. The method of claim 6, wherein thetiming advance is transmitted in a timing advance command, and thetiming advance command is associated with a first timing advancegranularity.
 10. The method of claim 9, further comprising: indicating asecond timing advance granularity to the UE different from the firsttiming advance granularity based on an identity of the UE, wherein theidentity of the UE comprises one of an industrial Internet of Things(IIOT) UE or a legacy UE.
 11. A method of wireless communication at auser equipment (UE), comprising: receiving timing information from abase station, the timing information configuring a local clock at the UEbased on a grandmaster clock of a time-sensitive network (TSN); sendingan uplink transmission to the base station after a downlink transmissionfrom the base station; and obtaining a round-trip time (RTT)compensation associated with adjusting the timing information based on aRTT that is measured using the downlink transmission and the uplinktransmission.
 12. The method of claim 11, the RTT is measured from abeginning of a frame of the downlink transmission.
 13. The method ofclaim 11, wherein the timing information is received via one ofbroadcast or unicast.
 14. The method of claim 11, wherein the RTTcompensation comprises a timing advance for adjusting the timinginformation received from the base station.
 15. The method of claim 14,further comprising: adjusting the timing information based on the RTTcompensation, the timing information being delivered to an upper layerof the UE.
 16. The method of claim 14, wherein the timing advance isreceived in a timing advance command, the timing advance commandassociated with a first timing advance granularity.
 17. The method ofclaim 16, further comprising: receiving a second timing advancegranularity different from the first timing advance granularity based onan identity of the UE, wherein the identity of the UE comprises one ofan industrial Internet of Things (IIOT) UE or a legacy UE.
 18. Themethod of claim 17, wherein the second timing advance granularity isfiner than the first timing advance granularity.
 19. The method of claim18, wherein the second timing advance granularity is preconfigured orreceived in a separate message from the timing advance command.
 20. Anapparatus for wireless communication by a base station, comprising: amemory; and at least one processor coupled to the memory and configuredto: send timing information to a user equipment (UE), the timinginformation configuring a local clock at the UE based on a grandmasterclock of a time-sensitive network (TSN); receive an uplink transmissionfrom the UE after a downlink transmission to the UE; determine around-trip time (RTT) compensation associated with adjusting the timinginformation based on a RTT that is measured using the downlinktransmission and the uplink transmission; and transmit the RTTcompensation to the UE.
 21. The apparatus of claim 20, wherein the atleast one processor is further configured to: receive informationindicating the grandmaster clock of the TSN.
 22. The apparatus of claim20, wherein the RTT is measured from a beginning of a frame of thedownlink transmission.
 23. The apparatus of claim 20, wherein the timinginformation is one of broadcast to a plurality of UEs or is unicast tothe UE.
 24. The apparatus of claim 20, wherein the at least oneprocessor is further configured to: adjust the timing information basedon the RTT compensation.
 25. The apparatus of claim 20, wherein the RTTcompensation comprises a timing advance associated with adjustment ofthe timing information transmitted to the UE.
 26. An apparatus forwireless communication by a user equipment (UE), comprising: a memory;and at least one processor coupled to the memory and configured to:receive timing information from a base station; send an uplinktransmission to the base station after a downlink transmission from thebase station; and obtain a round-trip time (RTT) compensation associatedwith adjusting the timing information based on a RTT measured using thedownlink transmission and the uplink transmission.
 27. The apparatus ofclaim 26, wherein the RTT is measured from a beginning of a frame of thedownlink transmission.
 28. The apparatus of claim 26, wherein the timinginformation is received via one of broadcast or unicast.
 29. Theapparatus of claim 26, wherein the RTT compensation comprises a timingadvance for adjusting the timing information received from the basestation.
 30. The apparatus of claim 29, wherein the at least oneprocessor is further configured to: adjust the timing information basedon the RTT compensation, the timing information being delivered to anupper layer of the UE.